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MISCANTHUS Practical Aspects Of Biofuel Development

ETSU B/W2/00618/REP URN 03/1568

Contractor Energy Power Resources Ltd

Prepared by Robert Newman

Subcontractors Bical Ltd Anglian Straw IACR - Rothamsted

The work described in this report was carried out under contract as part of the New & Renewable Energy Programme, managed by ETSU on behalf of the Department of Trade & Industry. The views and judgments expressed in this report are those of the contractor and do not necessarily reflect those of ETSU or the Department of Trade & Industry._____

Interim Report Published March 2002 Final Report Published November 2003 © Crown copyright 2003 dti Department of Trade and Industry EXECUTIVE SUMMARY

Project Objectives

• To plant and establish an energy crop of Miscanthus • Monitor and record it’s growth • Harvest the straw, bale it and deliver to the power station for a combustion trial. • Undertake a controlled trial and establish the key combustion characteristics. • Evaluate any change in power station performance andIPC compliance with baled Miscanthus as the fuel.

Background

The government has set an objective for a 10% contribution to UK electricity supplies from renewable sources by 2010. It is clear that if the UK is to achieve this then biofuel utilisation will have to increase substantially. EPR is a leading UK developer of renewable energy projects and is actively seeking to encourage and assist with the development of commercially viable alternative biofuels. With it's nearby 36MW Biomass Power Station near Ely, EPR could offer the opportunity of a long-term fuel supply contract if Miscanthus could be shown to demonstrate an ability to replace or supplement straw, without adverse restrictions.

Miscanthus is one of the most researched and most advanced, non-straw, biofuel crops. It has high yield, perennial growth and good disease resistance, although this has not been proven on a commercial scale. As a C4 crop it is considered to be an efficient converter of solar radiation to biomass energy under the right conditions.

To promote the use of Miscanthus, it was essential that its production, storage, handling and combustion be demonstrated on a commercial scale. This project has attempted to achieve this. The integration of biofuel crops and energy conversion has presented a unique opportunity to demonstrate the benefits of Miscanthus to potential UK growers and a wider international, technical audience.

Summary of Work

Work on this project has concentrated on three main areas:

• Modification of EPRL's Elean plant to accept and use miscanthus as a fuel • Miscanthus production, concentrating on planting, growth monitoring and future harvesting of the Miscanthus fuel. • Combustion trial of baled Miscanthus.

Modifications

Modifications were required at the Elean plant to enable the power station to accept baled miscanthus as a fuel. The mechanical handling system needed to be modified to ensure the introduction of miscanthus bales would not damage or restrict the plant.

i Two possibilities for introducing miscanthus into the facility were evaluated. Each method was designed and priced as a suitable alternative.

One possibility was to modify the plant allowing it to accept chopped miscanthus. Provision would be made for a covered loading area with a large storage pit with a purpose designed conveying system delivering metered volumes onto the straw feed lines and into the combustion system.

The capital cost to provide this system in its entirety would be close to the original total budget of £1.2m and would require a change to planning permission because of the revised building layout required.

A second possibility assessed the requirements and cost benefits of introducing Miscanthus in baled form into the plant. To achieve satisfactory operation, the design of the entire straw fuel handling system had to be modified to accommodate the physical differences between Miscanthus and cereal straw, i.e., the material bulk density and its abrasion characteristics. The crane system and feed conveyor design needed to be up rated to accommodate possible 850kg Miscanthus bales.

This design was inherently integrated with the existing plant layout and did not require any planning revisions.

The capital cost to achieve this modification was £190k.

Both options for plant modification were investigated thoroughly, with the advantages and disadvantages of each being considered. Several key factors in choosing the most appropriate option included: the efficient use of storage, transport costs, ease of handling, impact on power plant and firing techniques, impact on control systems and fouling potential and perhaps most importantly financing options.

By moving miscanthus in bales and firing as such into the main bale burners, any combination between 0 and 100% firing of miscanthus could be theoretically achieved. The chopped fuel option would be limited to a maximum of 25% due to existing furnace feed design.

The introduction of an independent chopped fuel mechanism would create the need for a much more complex control system and flame protection system, obtaining even combustion rates across the furnace could not be guaranteed. With the potential for slagging and fouling any localised high temperature zone could prove detrimental to plant performance and availability.

The most important point in the selection of the feed system for miscanthus was that of finance. Currently and at the time of consideration it was not possible to obtain clearance from our bank, within the timescale available, for the provision of an extra £1.2 million, unless the market for chopped miscanthus has been established. As establishment of the market is the purpose of this project and so this requirement clearly could not be met.

In light of these considerations it was decided that the project would go ahead with the baled system. The designs for the chopped system have been retained should the market for chopped miscanthus change and finance is more readily achievable.

ii Modifications for the receipt, transport and introduction of baled miscanthus were implemented during the last part of the Power Station construction.

Production of Miscanthus.

A suitable site for the trial plot was selected close to the Elean Power Station. The field is 12hectares in total and had been in continuous wheat production for a number of years. Two hectares of the field was set-aside for the Miscanthus growing trial. The intention was to grow the rhizomes for two years, then to harvest and split the rhizomes and replant an area of 7ha, so that at the end of the 4 year project there would be sufficient miscanthus for the combustion trial at the Elean Power Station.

In August 1999 planting of miscanthus was carried out using an adapted muck spreader with a density at about 2 to 2.5 rhizomes/m2. Conditions at the time of planting were poor, late in the season with dry weather and followed a recent wheat crop.

By the autumn there was reasonable growth on more established plants but the crop at this time was sparse, plant population was not spread evenly over the area and there were areas where no plants existed. A definite need to replant certain areas was identified in Spring 2000 and a new plan for replanting was produced. It was recognized that reestablishing at this stage meant that it would not be possible to plant an additional 5 ha in year three using existing rhizome stock, since the rhizomes would not increase sufficiently in bulk for splitting in one year. It was therefore agreed that additional miscanthus plots established under other initiatives would also be harvested to produce sufficient material for the combustion trial.

The trial plot was replanted in May 2000 under an improved planting protocol again using an adapted muck spreader. Establishment this time was more successful and much improved over the first trial plot. Weed control was better and the plants appeared healthy.

Progress over the late summer and autumn was slow while entering the winter period where plant survival rather than growth is of importance, but there was substantial growth over the summer of 2001, which continued throughout 2002.

Some valuable lessons have been learnt from this experience of establishing miscanthus at the commercial scale:

• The problems experienced with the establishment of the first phase of planting has illustrated that good quality rhizomes, stable soil conditions and appropriate commercial planting techniques are essential for good establishment. Rhizomes should be young, stored and transported under temperature-controlled conditions and they need to be kept cool to retain their quality. Good establishment is critically important.

• A muck spreader distributed the rhizomes satisfactorily however no other spreader types were used and therefore direct comparisons could not be made. A problem noticed at the site was that the spreader knocked off some developing shoots and this could have been avoided

iii if the rhizomes had been less advanced in shoot development at the time of planting. The planting method needs to be developed further.

• Plough design and depth control may not have been adequate for the conditions at the site. The late decision to go ahead with planting meant that the soil was prepared quickly, just before initial planting, without proper levelling and settling, which probably did not contribute to successful planting. The plough method used offers a cheap, quick and simple method of planting but more experimentation is needed to test the methods to identify improvements.

• Weed control measures are particularly important in the early stages of establishment.

• No significant pest or disease problems where identified, however inquisitive grazing by rabbits or hares was a problem in the first year of establishment.

Since the trial plot itself did not provide sufficient miscanthus for the combustion trial; this was overcome by harvesting miscanthus from other sites in the area around the Elean Power Station. Some harvesting at these other sites was undertaken in October 2001, to provide 32 bales of material for a bale handling trial.

The material for the combustion trial came from the trial plot at Witcham, which gave a yield of 7.3 t/ha and an additional 7 hectares of miscanthus from an ADAS site at Mepal and Anglian Straw sites at Ramsey and Willingham. The crops were 1 to 4 years old with a yield of 3 to 9 t/ha (depending on age). These produced a total of 99 bales of material weighing 53.3 tonnes.

Handling trial

The handling trial took place on the 23rd April 2002 and lasted for approximately 2 hours. The fuel provided a short-term test on the ability of the power station to take the Miscanthus at the full 100% firing rate. During the test there were no noticeable changes in the plant operating performance. The bales were easily picked up by the crane and easily transported on the conveyor mechanism.

During combustion of the miscanthus the plant did not lose any output, it remained steady, generating 36MW gross power at the turbine and exporting a net electrical power of 33 MW. The boiler drum pressure and steam flow also remained steady indicating no appreciable difference between Miscanthus firing and straw firing.

Combustion trial

The combustion test was undertaken generally in accordance with DIN 1942, a Europe wide accepted test code, for a continuous period of four hours. This required the supply of over 50 tonnes of baled miscanthus in the fuel barn, which was provided well in advance, ready for use.

iv Assessment of how Miscanthus performed was undertaken by comparison with conventional cereal straw against the following criteria:

• Ease of handling and conveying • Ease of chopping • Ease of entry into combustion chamber • Furnace temperature profile • Steam andElectricity production rates • Plant Chimney Emissions • Ash collection and removal • Operating stability, and • Sustainability and Availability

Handling results

• Both cereal and Miscanthus, in baled form, handled and conveyed in a similar manner • All baled materials chopped successfully although Miscanthus required a small increase in torque setting, indicating that it was slightly tougher to chop.

Combustion Test Results

Test results show an electrical export level over 36.5 MW, using between 6 and 6.5% natural gas by energy, at a boiler efficiency of above 90%, which is quite respectable for a plant of this size. The accuracy of measurement was high with less than 0.2% error.

No particular problems were encountered on either bottom ash or fly ash at any stage of the test and performance was very similar to cereal straw in terms of the key indicators: steam flow steam temperature, combustion efficiency, cycle efficiency and plant electrical output.

Units Cereal Start Mixed Cereal Cereal End & Miscanthus Electrical Export MWe 36.98 36.53 37.00 Boiler Duty MWth 102.84 102.64 102.63 Combustion Efficiency % 99.47 99.38 99.51 Boiler Efficiency Direct Method % 90.62 90.54 90.46 Boiler Efficiency Indirect Method % 90.59 90.40 90.55 Direct Method Error % +0.03 +0.14 -0.09 Cycle Efficiency % 32.59 32.22 32.61 Straw Specific Fuel Consumption kg/kWh 0.753 0.74 0.749

v Emissions

Designed with an overall cycle efficiency of +32.5%, the trial achieved around this level. All hourly emissions were well within limits and the plant was stable and controllable throughout. One short excursion occurred shortly after the start of mixed fuel firing as the plant control system settled to accept the new fuel mix.

Mixed Cereal Emission Units Cereal Straw Cereal Straw IPC Limits & Miscanthus Particulates mg/Nm3 110 19.0 112 25

SO2 159.7 146.3 2110 300 CO 112.1 100.0 612 250

NO 49.1 715 811 —

NO2 3.4 3.3 3.2 —

NOx (as NO2) 70.3 99.4 116.5 300 HCl 118 24.4 215 30 Dioxins ng/m3 ND ND ND 0.5

Lime Consumption kg/h 22.6 614 616 ---

Sustainability and availability

Due to the limited nature of the test work, covering a one-day trial only, the question of availability and sustainability of combustion is more difficult to establish. Given the very similar results and performance between the mixed straws and cereal straw, one could expect Miscanthus bales to provide good long-term results and could become a regular contract fuel.

Financial Implications

The cost of Miscanthus to the power station is fairly similar to cereal straw, on a delivered energy basis. Cereal straw being the cheapest normal supply material.

Cereal Miscanthus

Load & Deliver Cost £/tonne 174 9.10 £ / GJ 0.72 164

Total Cost £/tonne 3181 31.20 £ / GJ 2.29 120

* Total cost excludes any payment to the farmer for non-food crops grown on set aside land

vi Conclusions

This work has shown that Miscanthus can be successfully grown and harvested, with reasonable yield rates and provides a suitable alternative, similar priced fuel to conventional cereal straw for power plants such as Elean.

Operation of the Elean Power Station with Miscanthus caused no significant problems and performance was very similar to conventional cereal straw, providing much the same electrical export at much the same cycle efficiency.

In conclusion baled Miscanthus straw has sufficiently proven itself to burn efficiently, meet IPC limits and plant output requirements.

Anglian Straw would be happy to contract for Miscanthus in the same way as cereal straw.

vii GLOSSARY OF TERMS

Advanced Conversion Gasification, pyrolysis or anaerobic digestion, or any technologies with a combination thereof.

Biomass Is a fuel where at least 98% of the energy content is derived from plant, animal matter or other substances not derived from a fossil fuel. It includes such fuels as agricultural wastes, forestry wastes or residues, sewage and energy crops.

Cereal Straw Straw produced as a by-product of a cereal crop grown for consumption as food. Varieties include mainly wheat, barley and oats but could also include corn, maize and rye etc.

C4 The term ‘C4’ refers to plants, which have an additional metabolic pathway, for the transport of carbon dioxide, in the process of photosynthesis. Plants without this extra pathway are called c3, and include all U.K. crops except maize. C4 plants photosynthesise with greater net efficiency than C3 at high light intensities and high temperatures. They may also utilise water with greater efficiency. However at low temperatures, C3 plants may often photosynthesis with greater efficiency, although there are possibilities for genetic selection of C4 plants with improved cold tolerance.

Cycle Efficiency The ratio of electrical power exported to net heat supplied.

DIN 1942 A Europe wide accepted standard for undertaking and evaluating a steam generating boiler test on a given fuel.

Energy Crops A plant crop grown primarily for the purpose of being used as a fuel. This may be grown on set aside land provided it is not sold for consumption as food.

Gasification The substoichiometric oxidation or steam reformation of a substance to produce a gaseous mixture containing two or all of the following: oxides of carbon, methane and hydrogen.

GCV/NCV GCV = Gross calorific Value (kJ/kg or MJ/kg) NCV = Net Calorific Value (kJ/kg or MJ/kg)

NCV=GCV - 24.5 x (9 x % H2 + %%O)

The net calorific value takes account of the latent heat loss of evaporation of water to steam.

1 GSA This is a ‘Gas Suspension Absorber’ a specific type of acid gas cleaning system used at the Elean Power Station. It is capable of both dry and semi-dry scrubbing of acid gases (SOx and HCl).

Hay Straw from a non-cereal based product.

Hesston Bale A rectangular shaped bale of any given product having the following dimensions: Max 1.28 x 1.33 x 2.50 metres Min 1.22 x 1.27 x 2.25 metres Density 125-145 kg/m 3

Loss on Ignition Weight loss of combustible material in an ash sample

MCR Maximum Continuous Rating; this refers to the level of any plant criteria when operating at full output. e.g., steam flow, fuel flow, air flow etc.

MWe Electrical Energy

MWth Thermal Energy

Photosynthesis Synthesis of organic compounds in green plants from water and carbon dioxide using energy absorbed from sunlight with chlorophyll.

Pyrolysis The thermal degradation of a substance in the absence of any oxidizing agent (other than that which forms part of the substance itself) to produce char and one or both of gas and liquid.

Set Aside Land designated as ‘set-aside’ from food crop cultivation, for which the farmer has received an EU subsidy.

Straw Specific Fuel The fuel quantity required to produce 1kW of electricity; kg/kW, Consumption expressed as:

Fuel flow (kg/h) (100-% Nat Gas)/100*Exported kW/h

Where % Natural gas is % of thermal energy supplied

Triticale A common hardy hybrid variety of wheat and rye.

Vegetative Growth of plants by production of leaves, stems and roots prior to the formation of reproductive organs.

2 CONTENTS Page

EXECUTIVE SUMMARY

Project Objectives...... i Background...... i Summary of Work ...... i Modifications...... i Production of Miscanthus...... iii Combustion Test Results...... v Conclusions...... vii

GLOSSARY OF TERMS...... 1

1.0 What is Miscanthus?...... 7

2.0 The Elean Power Station...... 10

2.1 The Process...... 10 2.2 Design Plant Performance...... 14 2.3 Impact on Straw Production ...... 14

3.0 Power Station Modification...... 15

3.1 Options Considered...... 15 3.2. Summary of considerations...... 16 3.3. Consents...... 18 3.4. Modifications...... 18

4.0. Establishment of Miscanthus...... 19

4.1 Site details...... 19 4.2. Details of seed and site preparation...... 19 4.3. First Phase of Planting...... 20 4.4. First Phase of Miscanthus Establishment and Growth Characteristics...... 21 4.5. Second Phase Preparation and planting...... 21 4.6. Plant Growth and development...... 21 4.7 Bio Diversity...... 28 4.8 Discussion...... 29

5.0. Harvesting, Baling & Storage...... 31

5.1 Yield Rates...... 32 5.2 Material Handling Trial ...... 32

3 6.0 Combustion Trial - Fuel Data...... 37

7.0. Combustion Trial...... 39

7.1. Test Procedure ...... 40 7.2. Sampling and Recording...... 40 7.3. Test Results...... 44 7.4. Comments...... 46

8.0 Plant Performance...... 47

8.1 Energy Balance...... 47 8.2 Plant Emissions...... 47 8.3 Ash Details...... 53

9.0 Financial Implications...... 55

9.1 Straw Supply...... 55 9.2 The Price of Straw...... 55

10.0 Comments and Conclusions...... 58

10.1 Agronomy...... 58 10.2 Combustion Trial...... 59 10.3 Assessment...... 59

REFERENCES 62

APPENDICES

A1 Layout of Trial Plot at Witcham, Mepal...... 64 A2 General Grower Guidelines ...... 65 A3 General Comparison of Fuels...... 66 A4 Normal Operating Details of Ely Power Station...... 67 A5 Plant Instrumentation...... 69 A6 Test Procedures...... 70 A7 Overall Steam Cycles andEfficiency ...... 72 A8 Plant Emissions...... 75 A9 Details of Sub-Contractors...... 78 A10 Key Staff...... 79

4 INDEX OF TABLES

Table 4.2 Rhizome weight variation...... 20 Table 4.6.1 Growth Characteristics...... 22 Table 4.6.2 Wheeling Affects on Stem Height...... 26 Table 4.6.3 Changes in Stem Height in individual Plots in 2002...... 26 Table 4.6.4 Assessment of Rhizomes...... 28 Table 4.6.8 The Abundance of various Weeds in the fieldin Spring 2001...... 30 Table 5.1 Yield Rates...... 32 Table 5.2.2 Comparison of Handling Power Requirements...... 36 Table 6.1 Summary of Straw Supplied...... 37 Table 6.2 Analytical Results of Straw Samples...... 37 Table 6.3 Mixed Solid Fuel Analysis, as fired...... 38 Table 7.3 Test Results...... 44 Table 8.2 Emission Test Results...... 47 Table 8.2.1 SO2 & HCl Emissions...... 49 Table 8.2.2 Particulates Emissions...... 49 Table 8.3 Ash Analysis, by weight...... 53 Table 9.1 The Price of Straw...... 56 Table 10.1 Overall Cost of Straw by Weight & Energy Supplied...... 59

INDEX OF FIGURES

Figure 1 Miscanthus...... 7 Figure 2 Pattern of Branching in the growth of Rhizomes...... 8 Figure 3 EPR Ely, Straw Fired Power Station...... 9 Figure 4 Combustion System ...... 10 Figure 5 Seasonal Variation in Straw Consumption and Export Power...... 11 Figure 6 Seasonal Variation in Straw Moisture and plant Efficiency...... 12 Figure 7 Overall Process Flow Diagram...... 13 Figure 8 Reinforced Transfer Conveying System ...... 17 Figure 9 Cross Conveyor and Scarifier...... 17 Figure 10 Miscanthus plot at Witcham...... 19 Figure 11 Original Planting and Replanted growth after 2 Years...... 22 Figure 12 Miscanthus growth Rate ...... 23 Figure 13 Changes in Stem Density between 2000 and 2002...... 24 Figure 14 Stem Production Following Harvest Operations ...... 25 Figure 15 Changes in Stem Height between 1999 and 2000...... 25 Figure 16 Effect of Water Logging on Stem Growth in 2001...... 27 Figure 17 Examples of Rhizomes planted at Witcham...... 28 Figure 18 Unloading of Miscanthus into the West Barn...... 33 Figure 19 Un-sheeting of a Miscanthus Delivery...... 39 Figure 20 Collected Fuel Sample...... 42 Figure 21 Miscanthus - Ready for Transfer...... 42 Figure 22 Crane Transfer from Barn to Conveyor...... 43

5 Figure 23 Bag Filter System and Gas Suspension Absorber...... 51 Figure 24 Power Output and Oxygen Level...... 52 Figure 25 Straw Emissions, referenced to Limits...... 53 Figure 26 Straw Cost Variations with Moisture Content...... 56 Figure 27 Variation in Straw Consumption with Moisture Content...... 57 Figure 28 Overall System Diagram...... 73 Figure 29 Summary of Plant Emission Levels...... 76

6 1.0 What is Miscanthus

Miscanthus, sometimes called ‘elephant grass’, is a woody perennial that can be harvested annually. Because of its efficient photosynthesis mechanism, it has a higher yield potential than most other plant species grown in the UK with yields up to lOdt/ha. The crop takes approximately 3 years to mature in the UK and yields do not reach an optimum until this point. It is also considered to have a low nutrient requirement and relatively low moisture content on harvest, when compared with conventional cereal straw.

Figure 1. Miscanthus (ref: Wood Fuel Now, Oct 1993)

Miscanthus is a genus of woody, perennial grass that originated in South-East Asia. The rhizomes make up a highly branched storage system andthe roots usually penetrate at least a meter into the soil. Even though much of the below ground growth takes place in the first year, the crop usually

7 does not reach maturity until after two or three years. This crop does not make many demands on the soil and therefore is usually able to grow on different types of land.

There are 14 species within the genus Miscanthus (Hodkinson et al 1997), it is indigenous to Asia, geographic range from 50°N in North Eastern Siberia to Polynesia 22° and west to Kashmir and Nepal. Four species are found in Africa (Hodkinson et al 1997).

The grass has woody stems that dieback in winter and in spring new growth is regenerated from buds on underground rhizomes. In the UK and continental Europe most of the research has centred on M. giganteus. This is a naturally occurring interspecific triploid (N=57) hybrid between M. sacchariflorus andM. sinensis. M. giganteus is sterile and requires vegetative propagation to generate plant stocks. It possesses the C4 photosynthis pathway that makes it more efficient in the use of nitrogen and water than many temperate cereals and grasses (Brown 1978). Stems elongate very rapidly reaching 2-3 m in height in mature plants, taking several years to reach optimum yield.

A few varieties of M. sinensis have been evaluated, mainly in Europe. This species is a tufted perennial and stems grow l-2m. It is a flowering species producing an attractive flower like plume. Seeds can be fertile but present a very low level of establishment because they cannot ordinarily survive the winter conditions. However, M. sinensis is considered to be better adapted to cooler conditions than M. sacchariflorus.

Figure 2. Pattern of Branching in the growth of Rhizomes (Rutherford 1992)

8

2.0 The Elean Power Station

Elean is a 36 MW electrical generating station consuming around 200,000 tonnes of Hesston size baled straw. Situated near Ely, Cambridge it is the UK's first and only large-scale power station burning straw. It is Equipped with two large, fully enclosed, straw bams with weighbridges; automatic crane offloading and a fully automatic fuel feed system. It is a thoroughly modern Danish biomass design.

2.1 Process Description

Anglian Straw Ltd, manage deliveries to the plant and collect straw from farms within a fifty-mile radius of the plant. A truck will arrive at the power station every half an hour; the fuel is then automatically tested for moisture content as the bales are craned and weighed from the delivery trucks. The on site barns are capable of holding a total of 2,100 tonnes of fuel, sufficient for up to four days of operation.

The process involves cranes that automatically unload and feed the fuel conveyor system, serving the twin cutters and bale shredders en route to the four screw fed stoker burners. Straw is burned on a two-stage grate. Volatiles are liberated on the initial stationary phase with the balance of combustion occurring on a secondary vibrating grate. Up to ten percent of the energy supply is provided by two natural gas fired burners, which are automatically controlled and provide a stabilising heat source to ensure even furnace temperatures throughout the range of straw moisture levels, as fired.

Combustion System

10 Flue gases pass through an economiser and are neutralised by lime injection prior to their passage through a bag filter to remove particulates and acid gases. The resultant fly ash is rich in potassium and phosphate salts and is the basis of an organic fertiliser.

The boiler plant is a high temperature and high-pressure water tube design. A two second residence time at temperatures in excess of 850°C is maintained to ensure complete combustion and to ensure the destruction of dioxins and furans. Steam from the boiler is superheated to 520°C and 92 bar. The superheated steam flows to a high efficiency two stage-condensing turbine. The low- pressure turbine exhaust steam is then cooled and condensed in an air-cooled condenser unit. This unit operates under vacuum at an average 70mbar varying 50 to 90mbar, winter to summer, controlled by the ambient air temperature

Electricity is generated at 11,000 volts, some of which is used to run the in-house Power Station load (for fans and pumps etc), the remainder is sent to a step up transformer for export to the grid at 33,000 volts. The parasitic, in-house load is less than 3MW and the export capacity is 36MW, varying 32 to 38 from summer to winter.

The plant is expected to operate for around 8000 hours (91.3% of the year), allowing time for annual maintenance and further unplanned outage. The plant efficiency was planned to be between 32.0% in the winter and 32.2% in the summer. This assumed that the average moisture content of the Straw was 16%, ash content of 6.9% and a calorific value of 14MJ/kg and that a maximum of 10% of the combustion energy was from Natural Gas.

The following graphs, Figures 5 and 6, show the actual operational data for the year April 2001 to March 2002. This period covered the first year of operation from start-up.

oC,vw, 30000

25000 200000

20000 " % 150000 I0) 15000 S o ■g- c 100000 o 10000 i 0) IU 50000 5000

0 APR. MAY JUNE JULY AUG SEPT. OCT. NOV. DEC. JAN. FEB. MAR Month (2001/2002)

Straw Input -Electricity Output

Fig 5 Seasonal Variation in Straw Consumption and Export Power

11 19

18.5 c 18

14

% Efficiency % Moisture

Fig 6 Seasonal Variation in straw Moisture and plant Efficiency

12 33 Natural gas 32 H/ product and a6h handling 23 Water for aEemperatOrS 31 Straw barns 22 Superheater 3 30 Wood chip 21 Superheater 2 14 Combust Jon air Intake 7 Walor coofcd duel 29 Wood chip silo 2D Superheater 1 13 Forced draughl fan G Stoker 28 Fabric Filter 19 Economiser 12 I nd uceti draw grit fa n 5 FLrc damper* 27 Gae Suspension Absorber 1 e steam drum 11 Air p re neater ■i Scantier 2fi Fhie ga$ cooler 17 Feedwater tank 10 Combusllon chamber 3 Dosing unit 25 Aircooled condenser 16 Preheated comhuBtiopair $ Stag conveyor 2 Seal gale* 24 High pressure ateam to turbine >5 Air preheater B Vibrating grate 1 Chair conveyor

Fig 7 Overall Process Flow Diagram 2.2 Design Plant Performance

During June and July 2000 the Ely Power Station began receiving conventional Hesston bales and undergoing commissioning. It began the final stages of reliability and performance testing early in 2001.

The Power Station passed its MCR (Maximum Continuous Rating) test and achieved a significant level of efficiency above design, from 32% design value to 35% overall when firing with the full 10 percent natural gas.

Despite the supply problems caused by extreme wet weather in its first year, the power station continues to operate at full power, exporting electricity for over 8,000 hours per year at an availability of + 91.5%.

2.3 Impact of Plant on Cereal Straw Production

The quantity of cereal straw produced per year around the Ely Power Station prior to construction was: 25 mile radius approximately < 700,000 tonnes

75 mile radius approximately <4,000,000 tonnes

Three quarters of this straw was baled.

Prior to the power station around 80% of the straw was used as livestock bedding. The 200,000 tonnes of baled straw used at the power station has reduced this figure to 75% and has had, otherwise, little impact on the overall straw market. It is hoped that the introduction of miscanthus will help to redress this small change.

14 3.0 Power Station Modification

To provide a suitable miscanthus fuel supply in a form that can be readily accepted and easily burned required the fuel to be processed in some way prior to delivery to the Power Station. Two possibilities for introducing miscanthus into the facility were evaluated. The first possibility was to modify the plant allowing it to accept chopped miscanthus. The second option was to modify the plant to allow it to accept the extra weight of a large number of Miscanthus bales. For either option it was important that the modifications would prevent damage and not restrict the plant.

3.1. Options considered

The two ways of introducing Miscanthus into the facility were considered according to the form in which the material was to be presented, i.e., chopped or Hesston baled. Both methods were considered, designed and priced as suitable alternatives.

CHOPPED

The scope of this design extended beyond the horizon of just miscanthus; the provision of a complete facility for the acceptance of a chopped fuel would make it available for a number of other fuels such as wood chips and processed fuels such as RDF.

The chopped fuel design required the provision of a covered loading area with a 100m3 capacity storage pit, to provide capacity at weekends and periods of no delivery. Once in the pit, a horizontal auger will convey the fuel onto a series of elevating conveyors to a balancing silo (day hopper) located above the main straw feed system. From this silo, metered volumes of fuel will be fed into the central straw feed lines and into the combustion system via interlocked air sealed fire dampers.

The additional building required to house the loading area and storage pit required a significant change to the Planning Consent, which would present an unacceptable time delay to the project and add to the cost.

The capital cost to provide this system in its entirety was very expensive and close to the original budget of £1.2m. This would have left no money to complete the rest of the miscanthus work. This option was thoroughly investigated, however, but in light of the considerations outlined in section 3.2. ; it was decided that the project would not go ahead with this system.

This option assessed the requirements and cost benefits of integrating baled Miscanthus into the existing straw feed system. In order to achieve satisfactory operation, the design of the entire straw fuel handling system, from reception and storage to the furnace, had to be modified. This was required to accommodate the fundamental physical differences between Miscanthus and cereal straw, i.e., the material bulk density and its abrasion characteristics.

15 The crane system and feed conveyor designs required up rating from the 650kg cereal straw bale maximum to accommodate a possible 850kg Miscanthus bale. The structures were stiffened and high specification bale breaking screws were incorporated to mitigate the possible affects of increased material abrasion.

This design did not require any special planning revisions andthe capital cost to achieve this modification was £190k.

3.2. Summary of considerations

Both options for plant modification were investigated thoroughly, with the advantages and disadvantages of each being considered. There were several key factors that were deemed to be important in choosing the most appropriate modification option. These included: the efficient use of storage, transport costs, ease of handling, impact on power plant and firing techniques, impact on control systems and fouling potential and perhaps most importantly financing options.

It was agreed that on site farm storage of bales would be easier and utilise existing straw based equipment. Storage of chopped miscanthus on a farm would be difficult, it would take up valuable land space, require covering to prevent a wind blown nuisance and protect it from heavy rainfall.

A different high-sided road transport vehicle would have to be used to carry a load of lower density. Transport cost for chopped miscanthus would therefore be much more expensive.

By moving miscanthus in bales and firing as such into the main bale burners, any combination between 0 and 100% firing of miscanthus could be theoretically achieved. The chipped fuel option would be limited to a maximum of 25% due to the existing furnace feed design.

The control system and flame protection systems for an independent chopped fuel feed supply would be much more complicated and obtaining even combustion rates across the furnace could not be guaranteed. With the potential for slagging and fouling any localised high temperature zone could prove detrimental to plant performance and availability.

Evaluation of the miscanthus combustion trial was considered to be much easier with direct comparison made between baled straw and baled miscanthus. Particularly if straw can be stored and fired from one barn whilst miscanthus is stored and fired from the other barn.

The most important point in the selection of the feed system for miscanthus is that of finance. EPRL cannot currently obtain clearance from our bank, within the timescale available, for the provision of an extra £1.2 million, unless the market for chopped miscanthus is proven to be established. As demonstrating an establishment of the market is partly the purpose of the project this requirement clearly cannot be met.

16 Fig 8 Reinforced Transfer Conveying System

Fig 9 Cross Conveyor and Scarifier

17 In light of these considerations it was decided that the project would go ahead with baled system. The designs and costing for the chipped system has been retained should the market for chopped miscanthus change or if finance a more achievable goal.

Modifications for reception, transport and introduction of baled miscanthus into the combustion process with modifications to the crane and feed system, to allow denser, heavier Hesston bales were implemented in time during the last phase of construction of the Power Station.

3.3. Consents

The design for taking chopped miscanthus, as an alternative fuel source, had to be fully integrated with the main plant facility including the civil engineering implications, overall site layout and vehicle movements. This information was submitted to the local Planning Authority, East Cambridge District Council, for approval in mid June 1999.

Planning approval was granted without any additional conditions for the change to plant layout and for the use of baled miscanthus, provided current emission limits were met.

3.4. Modifications for the Baled System

The plant design was modified in the spring of 2000 to accommodate heavier Miscanthus bales and included:

Upgrade of cranes and associated equipment Upgrade of conveyors and stiffening of steelwork Smart card system to differentiate bales of Miscanthus (allowing greater flexibility) Upgrade of weighbridge

This new arrangement allows for miscanthus in baled form to be directly fired into any of the existing four bale burners without adversely affecting combustion or output of the plant.

18 4.0 Establishment of Miscanthus

4.1 Site details

An appropriate field was selected to hold the trial plot. It is situated on the outskirts of the village of Witcham, towards the village of Mepal, in Cambridgeshire. The field is in an ideal location as it adjoins the site of the El can Straw Burning Power Station.

The field is 12hectares in total and had been in continuous wheat production for a number of years. 2 hectares of the field was set aside for the Miscanthus field trial. The soil type is a clay loam, from which the usual spectrum of agricultural broad-leaved weeds, couch grass and some wild oats were expected.

Figure 10 Miscanthus Plot at Witcham, Showing Ely Power Station In the Background (after l1"1 phase of planting)

4.2 Details of seed and site preparation

Preparation of the site took place at the end of May 1999. The existing wheat crop was cut and baled for silage in order to remove all the green material that could hamper planting.

The soil was dry, as there had been very little rainfall in the preceding weeks. Moisture conservation was, therefore critical, particularly as it was late in the season for miscanthus planting.

The soil was disc harrowed five times in alternate ways in order to create some tilth. The miscanthus rhizomes needed to be in contact with fine soil particles to maximise take up of available moisture. The site was then power harrowed and rolled using a Cambridge ring roll.

19 The rhizomes were supplied by BICAL and were of the Giganteus variety. The rhizomes originated from the Dominican Republic and had been refrigerated en route from abroad and in storage in the UK. MAFF phytosanitary requirements for cleanliness and contamination were adhered to. The weights of the rhizomes were extremely variable. A random sample of 27 rhizomes saw a variation in weight of 1 to 60g (Table 1). The average weight of the rhizome was 17.1g, and the majority of rhizomes weighed within the range 1 to 20g.

Table 4.2 Rhizome weight variation

Rhizome Weight 1-10g 10-20g 20-30g 30-40g 40-50g 50-60g 8 18 22 37 60 10 15 26 58 7 13 25 10 17 10 20 6 11 9 18 7 14 4 16 1 13 6

A further sample of 48 pieces was checked for size and number of buds. The mean length was 140.8mm (range 21-373mm), with a mean diameter of 7.8mm. The average rhizome and number of buds per rhizome was 1.88. No link could be observed between length of rhizome and number of buds present on the piece. There was on average 1.46 branches per piece, 42% were unbranched.

4.3. First Phase of Planting

Planting took place in May 1999, with a seed rate of 2.5 rhizome/m2 or 25000 rhizome/ha. A rear discharge, hydraulic floored muck spreader was used to plant the rhizomes, calibrated to spread the required seed rate. Calibration was calculated using the forward speed, width of spread and speed of the floor given that a box contained 400 rhizomes. The floor slatting was set at 300mm, although the recommended rate was 500mm. Gearing was adjusted at alter the bed speed to compensate.

The speed rate varied between 2 to 2.5 rhizomes/m2. This was measured by checking plant density in three positions behind the spreader:

1. Immediately behind the centre line 2. 1.5m from the left wheeltrack 3. 1.5 m from the right wheeltrack

After each pass of the spreader the rhizomes were ploughed into a depth of 10cm using a seven furrow shallow plough, in order to prevent them drying out. The time period between spreading

20 and ploughing in was between 30 - 45 minutes. The soil was then rolled immediately to further conserve soil moisture. The previous soil cultivations made it difficult to maintain direction and depth of ploughing. This has created some patches of unevenness in the tilth around the field trial. Inevitably some ends of rhizomes are left exposed.

At planting the weather conditions were 16 - 18°C, sunny with overcast periods, windy, good drying conditions. Within 5 days of planting 37mm of rain had fallen soaking the soil to a depth of 10cm.

4.4. First Phase of Miscanthus Establishment and Growth Characteristics

Monitoring from between 45 and 164 days after planting identified an emergence that continued to be patchy with some plants up to 70mm tall, with many others less than half this height. The achieved establishment was therefore not as good as originally anticipated. The crop was sparse and would require several years to increase density sufficiently to cover the whole of the field. Plant population was not evenly spread andthere were areas where no plants existed. The overall effect was unsatisfactory.

The plot had long suffered from inquisitive grazing, by hares that were attracted to the young plants and new shoots. Weeds were recognised as a problem but their treatment at this stage was deemed unnecessary since winter was approaching they would die down naturally and those that didn’t would help to provide some protection from frost and snow.

Growth had been good in some places, patchy in others with little or no growth in the remaining areas. The main areas for concern were the centre of the field andthe competition from weeds. It was agreed, therefore, that the whole plot would be re-established with new rhizomes and BICAL were asked to replant using best available practice for site preparation and planting.

4.5. Second Phase Preparation and planting

Preparations were started early during this second phase to ensure better planting conditions. The weed killer Gramoxone and a 17.17.17 (N:P:K) fertilizer was applied 6 weeks prior to replanting; the field was cultivated and more rhizomes planted. Replanting was undertaken in May 2000, at a planting rate of approximately 3 rhizomes/m2, with a shallow plough 2-4 inches deep. Individual rhizomes averaged 84 mm in length and weighed an average of 29g. Following replanting the land was rolled, with a tractor on terra tyres, which tended to compact the soil surface.

Grower guidelines were produced by BICAL that provided the basis for the growing and tending regime (Appendix 5).

4.6. Plant Growth and Development

Early growth (June and July 2000) was successfully established and the field was in better shape overall than in the previous year. Rainfall was high over the spring, which may have affected growth. The plant population was about 0.5 plants/m2 and was variable over the site.

21 A method of recording growth was established whereby the three plots previously established, to provide continuity to the assessments, were re-established in the same places. These plots were set at a stagger across the field (Appendix 1) and measurements were made randomly on plants within the plots. In 2001 and 2002 marked plants were used throughout the growth period.

Progress between July and September 2000 was encouraging, all plants looked healthy and vigorous with no evidence of disease. There was no significant change in the number of plants but shoot height had increased from 39cm to 100cm, an average of 0.9 cm per day. Some fully emerged leaves were more than 100cm in length and 2.5 cm wide, at mid leaf point, with many young shoots present.

There were still bare patches in the field; with the main areas of concern being the centre of the field, the northern edge along the hedge and the main entry point of the field. There were still some un-germinated rhizomes half submerged and lying on top of the soil in these bare patches. Some were plants still emerging, but the majority were in the range of 1.0 - 1.5 m tall.

Table 4.6.1 Growth Characteristics

Date of Measurement July 22nd September 27th Plants m2 0 33 0 33 Shoots m2 0 56 3 68 Height cm 39 1 100.4

Figure 11 Shows Original Planting and Re-Planted Growth after 2 years (Yardstick shown is to a height of 1.35m)

22 Days After Planting

Fig 12 Miscanthus Growth Rate

4.6.1 Stem density.

Between spring 2000 and 2002, stem density increased more than 90-fold. The largest increase was in 2001 and 2002 (Figure 13). Each year shoots emerged mainly in the spring and early summer period. In 2002, there was a higher stem number at the beginning of spring growth than at the end of the previous growth period.

Effect of wheeling on stem number.

In spring 2002, plants that had been either wheeled or unwheeled during earlier harvesting operations were marked and monitored during the growth period. Shoot emergence and stems per plant were unaffected by wheeling and remained so throughout the growth period (Figure 14).

23 25

20

Date

Fig. 13 Changes in stem density between 2000 and 2002.

4.6.2 Stem height.

Height measurements made before 28th June 2000 were to the peak of the leaf curve of the last expanded leaf Subsequently measurement was to the collar (ligule) of the last expanded leaf The change was made due to leaf movement on the windy site.

Stem height increased every year reaching over 2m in 2001 and 2.4m in 2002. Stem elongation was rapid every year except 1999 (Figure 15). In the earlier years many stems did not grow vertically probably because there was little between-plant competition but by 2001 decumbent stem growth had almost ceased.

Measurement to the collar understates stem height and actual height of stems can be estimated by adding 50cm to values given in the figures and tables. In 2001 and 2002, some stem heights were even greater because flowers emerged (Figure 17).

24 □ Unw heeled

□ Wheeled

20-Apr 15-May 13-Jul 24-Aug 28-Oct 2002

Fig 14 Stem production following harvest operations.

* —2000 e—2001 * —2002

Year

Fig.15 Changes in stem height between 1999 and 2002.

Effect of wheeling on stem height, 2002.

The average height for unwheeled and wheeled plants was similar on two of the three plots and on plot 3 an interaction with water logging may have affected growth (Table 4.6.2).

25 Table 4.6.2 Wheeling affects on stem height in 2002.

July August November Plot unwheeled wheeled unwheeled wheeled unwheeled wheeled 1 130 132 181 187 230 228 2 128 127 198 196 233 246 3 108 142 223 182 225 266 Mean 122 134 201 188 229 247

Effect of winter water logging on stem height.

In the winter of 2000 and spring of 2001 parts of the field near to the road were waterlogged. This affected plot 3 frequently, plot 2 intermittently and plot 1 was not affected (winter wet). Initial measurements made during 2001 found water logging did not kill plants but stem growth was affected by water logging. Stems initially grew more slowly on plot 2 and plot 3 than on plot 1.

Differences in stem height between plot 1 and plots 2 and 3 were significantly different in June and between plots 1 and 3 in July. Although stems on plot 1 remained taller for most of the summer, growth on plots 2 and 3 was more rapid and stems on these plots were taller in November, (Figure 16). After the winter of 2001/2 when water logging occurred again, differences in growth rates were again evident but summer growth compensated resulting in better growth on the wetter areas later in the year (Table 4.6.3).

Table 4.6.3 Changes in stem height (cm) on individual plots in 2002.

Plot June July August October 1 88 131 184 229 2 78 128 197 239 3 64 125 203 246

26 250 c □ 30-Jun 200 4-f ■ 21-Jul u> 150 o □ 18-Aug 100 □ 06-Oct o 5) ■ 10-Nov

Winter Intermittent Wnter w et waterlogging waterlogging

Winter condition

Fig. 16 Effect of winter water logging on stem growth in 2001

4.6.3 Weed Control.

The short time available in 1999 to remove the previous crop and cultivate the soil before planting prevented adequate preparation of the field to minimise weeds. After planting, a wide range of broad-leaved weeds germinated as well as patches of grasses. In 2001 a springtime assessment showed the range of broad-leaved weeds present (Table 4.8). The weed flora is typical of fields under arable crop management.

The majority of the weed species are annual or biennial but the presence of elder, a deciduous shrub of woodland and hedgerows, established because no harvesting had, so far, taken place. Weeds in the area subjected to winter water logging were less than elsewhere. Weeds have been a greater problem at the site than would normally be the situation in a Miscanthus crop. In a crop with a normal spatial distribution of plants, weeds would be out-competed by the rapid growth of the crop and shading created by the tall canopy. Surface litter from shed leaves would also contribute by the suppressing of weed germination.

4.6.4 Rhizome assessment

A rhizome assessment was carried out during this period. Six rhizomes were dug from random points in the field. The plants were selected as single stand plants. Rhizomes were washed to remove soil and weighed to obtain fresh weight. Four plants were dried in an oven at 80°C and dry weight determined. Two plants were kept whole, the number of shoots was counted ant the rhizomes were photographed. The purpose of this assessment was to establish the rhizome size and weight one growing season after replanting. Thirty pieces of rhizome were also measured at the time of replanting.

The assessment was made with caution as the rhizomes dugwere of two different ages (1999 & 2000) but it did give a general indication of how much the rhizomes had grown during the year.

27 Fig. 17 Examples of Rhizomes planted at Witcham

Table 4.6.4 Assessment of Rhizomes

Rhizome Fresh weight (g) Dry weight (g) Moisture % 1 734 9 155.7 78 8 2 32E3 73.1 77.2 3 463 4 102.4 77.8 4 232.2 47.5 79 5

5 a 147.6 - -

6 a 689 2 - - MEAN 431.4 94? 78]P

a photographed plants b average of 4 plants

The average rhizome weight at replanting was28.8g (ranging 7 to 58.9), compared with the original planting weight of 17. Ig (ranging 1 to 60g). The above table indicates a growth in body weight of up to 15 times, which would be expected given the increase in shoot density and height over the same period.

4.7 Biodiversity.

The field has provided a habitat for a number of different animals and birds. Hares were frequently seen in the field in the first 2 years. None have been seen recently but their droppings (or possibly rabbits) can be found. The height of the crop now makes it impossible to see more than a few metres in any direction. Foxes visiting the field have been reported by a person living nearby. In two years red-legged partridge have reared chicks in the crop and pheasants have also been seen in the field. Their choice of the field shows that the crop could provide suitable cover for game birds

28 except that beating through the crop would be difficult and unpleasant. Small birds and butterflies have been abundant probably feeding on weed flowers, seeds and insects on the plants.

Animals have caused little damage to the crop; rabbits or hares have sometimes grazed tender shoots but damage stopped once stems elongate, hence damage has mainly been confined to the spring and very occasionally later when new shoots appear.

Game birds might not use the field so much if the crop was denser because birds would lack flight areas. These could be provided either within the field or around the periphery. The terms of the planting grant for Miscanthus permits 10% of the field to remain uncropped to provide open space that could be used for improving biodiversity.

4.8 Discussion.

Lessons learnt at Witcham about how to plant Miscanthus rhizomes have been useful in developing planting strategies. Although the number of established plants was low the population has been maintained throughout the project. Plants have grown well and development has been comparable to plants grown elsewhere in experimental plots. Stems per plant are similar to values reported elsewhere. Harvesting in 2002 created extensive wheel marks across the field that could be clearly seen later in the year. However plant growth afterwards was not affected.

Monitoring growth has shown that most shoots emerge in the spring and early summer except in the planting year. The contribution to stem density from late season shoots was negligible. Late emerging shoots may die possibly from shading in the older crop (figure 13). This growth characteristic means that a greater uniformity of stem size is present at harvest.

Some new shoots for the next season are evident by late summer and if they grow too much before the winter they are vulnerable to frost damage. However the majority of stems arise from buds deeper in the soil and these were unaffected by frost or wheel damage and this could be the reason why wheeling did not affect growth.

The fact that water logging did not kill plants is a very positive finding but soil water logging is detrimental to harvesting operations and its timing. Water logging did affect stem growth and it was evident that differences between plots were related to the length of time that plants were subject to winter water logging. In 2001 and 2002, stem height was shorter at the end of the summer on the plot not affected by water logging. This suggests that soil water reserves were better on the other plots and supported better growth. But it might also be a topographical effect with water draining to the area from the drier bank on which plot 1 is situated.

Pre-planting strategies for weed control could not be carried out because of the brief period available for planting after the wheat had been removed and this probably contributed to the level of weed infestation. Also weed suppression by the crop was not very effective because of the low plant density. The result demonstrates the value of good weed control prior to planting and the importance of a high plant density and good spatial distribution.

29 Table 4.8 The abundance of various weeds in the field in spring 2001.

Common name Botanical name Very abundant Thistles Cirsium spp Groundsel Senecio vulgaris White campion Silene alba Redshank Polygonum maculosa Less abundant Chickweed Stellaria media Black bindweed Polygonum convululus Cleavers (Bedstraws) Galium aparine Spear thistle Cirsium vulgare Occasional Teasel Dipacus fullonum Mayweeds Matricaria spp Black-grass Alopecurus myosuroides Elder Sambucus nigra Lesser celandine and creeping buttercup Ranunculus ficaria and R repens Common couch grass Elytrigia repens Shepherds purse Capsella bura-pastoris

30 5.0 Harvesting, Baling & Storage

Work on this aspect of the programme was unfortunately delayed due to replanting of the Miscanthus rhizomes. It was originally hoped that the trial plot would yield 10 to 15 tonnes per hectare, sufficient for a 2-hour combustion trial, however the trial plot itself did not provide sufficient Miscanthus. This difficulty was overcome by harvesting miscanthus on a variety of other sites in the area around the Elean Power Station, and the quantity required was increased to allow for a 4-hour trial to ensure sufficient time for combustion establishment and comparison with cereal straw.

Early harvesting of these other plots was undertaken in October 2001 to provide material for a handling trial. This was accomplished using a mower conditioner and rape swathe, with baling undertaken within a few weeks of this. The swathe left stubble that ranged from 10-20 cm tall. The yield was confirmed between 6-9 t/ha.

There was also between 8 and 12 hectares of miscanthus available from these other sites that provided the additional material for a trial burn. These sites include EPRL's site at Witcham, ADAS sites at Mepal, Elton andBoxworth plus an Anglian Straw site in Peterborough. Bales were collected on site and, if possible, stored on site in one of the adjacent barns. Fuel delivery costs were then estimated using existing data on these three sites.

While harvesting, trailers, balers and lorries used to handle straw can cause soil compaction, particularly in a wet year. Compaction can have a major impact on yield that may not be possible to remedy in one year, leading to loss in yield for two or even three years. It was important to ensure that this impact is minimised, as far as was practicable, for the trial plot as miscanthus is a limited resource that cannot be easily replaced or improved. Harvesting of the trial plot was therefore not undertaken until soil conditions were sufficiently dry.

Harvesting for the final combustion trial was undertaken one week prior to the test. Natural over winter desiccation with two days drying in the swathe saw bales registering 10 to 16% moisture. The method and practice adopted was the same as that for the original handling trial although the weather at the time was dry with good soil conditions to allow easier field access, operation and removal. This can be seen from the much dryer straw produced for the combustion trial with 14% moisture compared to the handling trial at 22%.

As with cereal straw, a steel flail conditioner, in the exit chute of the mower, was used to fracture the stalks. This was not particularly effective on Miscanthus, which is quite woody and tended to produce long, strong lengths of material for the baler. In hindsight a second conditioner may have been more effective. After mowing the stubble was left at less than 10 cm.

Harvesting at the trial plot in Witcham utilised the full 2 hectares of growth, at the other sites a similar area was utilised to give comparison in number of bales collected. Since the requirement was for a total of around 50 tonnes it was not necessary to harvest the full areas available. The plot at Ramsey for example had around 20 ha available and could have provided all the fuel required. These other sites also had Miscanthus of different ages varying 1 to 4 years oldwith stem heights varying 2 to 4m.

31 Regardless of age or height baling was difficult because of the strength of woody material contained within the crop.

5.1 Yield Rates

From the various sites listed in table 5.1, 99 bales were collected of which 5 bales failed to meet the EPR bale specification as they were out of shape with tie strings being mechanically unstable. Three of these bales were successfully re-baled but two could not. The total of 99 bales was reduced; therefore, to 97 and these were transported directly to the power station for the full combustion trial.

Table 5.1 Yield Rates

Approx No. of Hectares Location Crop Age Crop Bales tonnes t/ha Harvested Height m Collected

EPR, Witcham 3 yr 3.3 27 2 14.54 7.3

ADAS, Mepal 1 y r 2.2 9 <2 4.85 3.0 Ramsey 1 y r 2.0 15 2 8.08 4.0 Elton 4 yr 4.0 44 <3 2169 8.8 Willingham 1 y r ND 4 ND 2.15 ND

Totals 99 53.31

5.2 Material Handling Trial

The handling trial, using material from the first small harvest, took place on the 23rd April 2002 and lasted for approximately 2 hours. The fuel provided a short-term test on the ability of the power station to take the Miscanthus at the full 100% firing rate. Information gathered from this trial was then used to assess the requirements for the full combustion test.

Arthur Rickward at Mepal provided thirty-two bales for the test. These included some harvested 6 weeks previously and some bales that were up to two years old. The older bales were uniform in shape but of a grey, very weathered and partially composted appearance. The new Miscanthus bales were bright and light yellow in appearance, but the bale shapes were not ideal This year's Miscanthus was baled using a swather, which resulted in longer strands of material that did not compact sufficiently to maintain a uniform shape.

Twenty-four selected bales were loaded onto Anglian Straw transport vehicles, in the field, by a suitable bale loader. These bales were moisture checked using a Protimeter moisture probe and inspected for bale shape and unwanted inclusions such as soil and grass plus any impact from birds

32 or rats. Some soil and grass was found on a few of the older bales, taken from the top layer, but there was no evidence of attack from birds or rats.

The vehicles were netted andtaken directly to the Power Station at Ely where they were weighed and moisture readings by the plants microwave system was taken.

Moisture probe readings indicated that the moisture levels had increased significantly in the older bales, showing an increase from 22% to 44% in some bales. There was also an obvious difference in appearance between the older and more recently baled material.

It was observed that the miscanthus bales from last year had faired better in the relatively small stack than conventional wheat straw may have done. A three high stack of wheat straw last year would have lost the top two rows and some of the bottom bales dueto water ingress. In the miscanthus bales only the top level of bales were lost.

Of the thirty-two bales available, eight were rejected primarily on the basis of their moisture content. Readings varied between 27 - 40% averaging, at approximately 30%. Twenty-four bales were accepted, with moisture readings between 8-26%, averaging approximately 18%.

5.2.1 At the Plant

The bales were delivered to the fuel reception barn, netting removed, weighed by the crane unloading system and their moisture levels recorded. The bales were temporarily stored in the barn before transfer to the main conveyor track for feeding both sides of the boiler, providing short term 100% Miscanthus firing.

Fig 18 Unloading of Miscanthus Bales Into the West Fuel Barn

33 During the test, which lasted for approximately two hours, there were no noticeable changes in the plant operating performance. The bales were easily picked up by the crane and easily transported on the conveyor mechanism. There have been some problems with the conveyor when higher moisture content straw has come into the plant. The conveyor chain link will rip through the bottom part of a bale if the fuel is damp and is then unable to carry the bale forward, this was not observed with the miscanthus bales.

As the bales moved through the plant important electric drive motors were monitored at strategic locations along the fuel transport line. They showed no significant difference in operating power levels during the Miscanthus handling trial compared to straw. The older Arthur Backward Miscanthus had been weighed following baling, prior to being stored in the field, and each bale averaged around 800 kg weight. After 2 years storage the crane weighed these bales, including the newer Miscanthus, at around 500kg per bale. This is much more in line with conventional straw. EPR had expected the fuel handling equipment to use more power to feed the heavier bales, but this never materialized.

There were some problems with the more irregular shaped bales that tended to jam at bends in the conveyor system. This, however, is quite normal for out of shape bales and they were overcome speedily and caused no significant problems.

The bale cutter (scarifier) for feeding the furnace had no problems in cutting the bales but the torque required to do so had to be increased for bales containing the newer Miscanthus, with thick long strands. The older material was quite brittle and easier to chop. Apart from this the scarifier worked well throughout the trial.

5.2.2 Combustion

From the scarifier the fuel, straw or Miscanthus, was blown into the furnace, just above a vibrating grate. Miscanthus, being a denser material than straw, was expected to require a longer period of burning on the grate. This was found to be the case in practice and so the vibration rate was slowed down to allow the miscanthus material to burn for longer. If more time had been available some small adjustments to the primary and secondary air settings would have also been made. Influencing factors such as grate residence time and air settings are firstly observed by viewing the grate, then inspecting the grate ash for unburned material and finally by laboratory analysis of grate and fly ashes.

During the trial the plant did not lose any output, it remained steady, generating 36MW gross power at the turbine and exporting a net electrical power of 33 MW. The boiler drum pressure and steam flow also remained steady indicating no appreciable difference between Miscanthus firing and straw firing.

5.2.3 Conclusions

The Miscanthus handling and combustion proving trial was reasonably successful although it would have been useful to have used 800 kg bales rather than 500 kg. The fact that the plant is currently set up to burn 500kg bales is probably the reason that the fuel firing rate and fuel to air ratios did not need changing to any significant degree.

34 Long hard pieces of miscanthus should in some way be broken into more manageable sizes prior to baling if the full bale shape and density is to be obtained.

There were no problems encountered with the loading and delivery of the bales of miscanthus and the crane system operated as normal on their receipt.

35 Table 5.2.2 Comparison of Handling Power Requirements

FEED BUFFER BELT - Straw Miscanthus ECA22AF001 Low High Frequency (Hz) 50 (average) 50 60 Current 11.5 +/- .25 8.4 9.51 Power (%) 69.5 36 47

SEAL BELT - Straw Miscanthus ENA41AF001 Low High Low High Frequency (Hz) 49(average) 48 49 Current 2.9 3.4 2.93 3.18 Power (%) 22 24 20.15 48.63

SCARIFIER Straw Miscanthus Low High Low High Frequency (Hz) 20.6 20.8 24 26 Current 15.6(average) 15 16 Torque 16 19 14 19

BurnerHHA4OAF001 Straw Miscanthus Low High Low High Frequency (Hz) 43.39 (average) 38.9 Current 10.18 (average) 10 Torque 5.83 7.55 6.4 7.55

BurnerHHA3OAF001 Straw Miscanthus Low High Low High Frequency (Hz) 35 39 Current 10.11 10.14 10.15 Torque 192 4.40 4.33 5.16

36 6.0 Combustion Trial - Fuel Data

For the full combustion trial samples of cereal straw and Miscanthus were taken from the vehicle deliveries and analysed by an independent laboratory. Moisture measurements were taken directly from bale moisture readings in the fuel barn, also from each delivery, using the plant’s microwave moisture measuring system.

Table 6.1 Summary of Straw Supplied

Mixed Cereal Cereal Straw Cereal Straw & Miscanthus Test Period hours 2 4 2

No. Of Cereal Bales Burned 102 111 110 No. Of Miscanthus Bales Burned 0 97 0 Average Bale Moisture % 13.9 14.09 13.9

Miscanthus Bale Weight k g — ——— 539 —— — — Cereal Bale Weight k g 503 503 503

Ratio of Cereal to Miscanthus 100 : 1 51.7:48.3 100 : 1

Natural Gas Fired Energy % 6.02 6.08 6.45

Bale density is an average for the whole test period.

Table 6.2 Analytical Results of Straw Samples

Ultimate Analysis Units Cereal Straw Miscanthus

Carbon % weight 45.13 45.73 Hydrogen db 5.47 5.70 Nitrogen 0.53 0.46 Chlorine 0.42 0.39 Sulphur 0.16 0.11 Oxygen 41.27 41.06 Ash 7.02 6.55

Calorific Value Net CV MJ/kg, db 16.5 17.3 Moisture % af 14.30 13.90

37 Table 6.3 Mixed Solid FuelAnalysis, as fired

Units Mixed Cereal And Cereal Straw Miscanthus

Carbon % weight 39.26 38.86 Hydrogen af 4.89 4.71 Nitrogen 0.39 0.46 Chlorine 0.35 0.36 Sulphur 0.09 0.14 Oxygen 35.28 35.53 Ash 5.65 6.04 Moisture 14.09 1190

Net CV MJ/kg, 14.18 1179

Note: af = as fired, db = dry basis, NCV- Net Calorific Value

38 7.0 Combustion Trial

The reasons for choosing the Elean Power Station plant is firstly that Miscanthus is believed to bum in a similar fashion to straw, indeed it has a similar fuel analysis. The Power Station is strategically placed in a potential large scale growing area for both straw and miscanthus and it is the only suitable recipient for this baled fuel.

The objectives of the Combustion Trial were:

• To confirm that Miscanthus in baled format can provide a practical and cost effective method of fuel handling

• To confirm the combustion of Miscanthus in commercial quantities did not impose any operational constraints, or result in adverse financial impact. This was achieved by substituting up to 50% of the total straw feed to the plant, for the duration of the burning trial. Using up to 50% miscanthus in the fuel for the test period is appropriate as this is the maximum proportion of miscanthus EPR foresee using in the fuel during normal plant operation.

Fig 19 Miscanthus delivery being unsheeted for the Combustion Test

39 During the trial burn it was hoped to demonstrate that miscanthus is a suitable alternative fuel for the Power Station, that it can be harvested, baled, transported and handled by the plant equipment in the same way as straw. Also to confirm that miscanthus is comparable to straw in terms of maintaining plant efficiency and out put. Performance of the plant, particularly in terms of efficiency and emissions, were continually monitored and the results trended to identify any deleterious affects resulting from the introduction of Miscanthus. Additionally, any abnormal plant disruption, additional manpower requirements or evidence of poor combustion were recorded.

A 50:50 split represents the maximum acceptable firing ratio, on a batch basis, that the Ely plant could reasonably maintain to provide sufficient proof of at least a 20% Annual Capability.

7.1 Test Procedure

The combustion test was undertaken generally in accordance with DIN 1942, a Europe wide accepted test code, for a continuous period of four hours. This required the supply of over 50 tonnes of baled miscanthus in the fuel barn, which was provided well in advance, ready for use. The plant was maintained for a period of several hours on conventional straw prior to change over to duel fuel firing.

The test continued until the miscanthus ran out and the plant forced to return to full cereal straw firing, this provided approximately four hours operating data. Data logging continued for a further three hours to record how the boiler recovered and to note any impacts on performance due to the miscanthus burn.

7.2 Sampling and Recording

• Plant - Data was continuously recorded by the plant plc system during the test and printed out at the end. A steady operating period of four hours was selected from the data and used for analysis.

• Fuel - Fuel was sampled from both the straw and miscanthus and aggregated (independently), for the analysis period. The number of bales consumed was determined from the delivered weights and average bale densities.

• Ash - Samples were taken and aggregated in the same manner.

• Emissions - Data was recorded and trended showing IPC requirements before, during and after the trial and reported in half hourly averages.

Assessment of how Miscanthus performed was undertaken by comparison with conventional cereal straw against the following criteria:

• Ease of handling and conveying • Ease of chopping • Ease of entry into combustion chamber • Furnace temperature profile • Steam andElectricity production rates

40 • Plant Chimney Emissions • Ash collection and removal • Operating stability, and • Sustainability and Availability

41 Fig 20 Collected Fuel Sample, size indicated by a 2p coin

Fig 21 Miscanthus Ready for Transfer

42 Fig 22 Crane Transfer from Barn to Conveyor

43 7.3 Test Results

Average Plant Operating Data Cereal Straw Mixed Cereal Cereal Straw 24/04/2003 Units & Miscanthus 10 - 12 h 12-16 h 16 - 18 h Operating Period hours 2 4 2 Cereal bales Consumed 101.7 111.2 110.1 Miscanthus Bales Consumed 0 97 0

Miscanthus Burned k g 0 52,232 0 Cereal Straw Burned k g 55,670 55,920 55,405

SolidFuel Consumption tph 27.84 27.04 2170

Miscanthus % weight 0.00 47.41 100 Cereal 98.23 50.76 9110 Natural gas 1.77 1.83 1.90

Electrical Export Gross MWe 39.58 39.15 3160 Electrical Export Net MWe 36.98 36.53 3100 Plant Running Load MWe 2.60 2.63 160

Average gas burned kg/s 0.139 0.140 0.149 Nat. Gas NCV MJ/kg 49.1 49.1 49.1

Total Straw energy burned MWth 106.64 106.47 106.14 Total Nat Gas energy burned MWth 6.835 6.886 1316 Total Fuel Energy Consumed MWth 113.48 113.36 113.46

Gas Firing by energy % 6.02 6.08 6.45

Overall Plant Cycle Efficiency % 32.59 32.22 3161 Boiler Duty MWth 102.84 102.64 10163 Blow down Loss MWth 0.204 1203 1210 Soot blower loss MWth 0.000 1000 1000

STEAM Flow tph 142.85 142.56 14156 Pressure bar 91.5 92.4 913 Temperature °C 519.9 520.1 5212 Blow down Rate % 0.95 194 198 Heat in Steam MWth 136.356 136.081 136.081 Heat Lost to Blow down MWth 0.204 1203 1210

FEED WATER Flow tph 144.20 14190 14195 Pressure bar 118.5 118.5 118.5 Temperature °C 196.6 196.6 1916 Heat in Feed water MWth 3172 3165 3166

44 Average Plant Operating Data Cereal Straw Mixed Cereal Cereal Straw 24/04/2003 Units & Miscanthus 10 - 12 h 12-16 h 16 - 18 h

Total Air Flow tph 162.5 163.1 162.7 Overall Excess Air % 18.7 19.6 19.0 Air Temperature °C 127 129 128 Air Humidity kg/kg da 0.012 0.0125 1012 Energy in Preheated Air MWth 4.71 4.82 4.76

Econ. Gas Exit Temperature °C 245.5 247.8 2419 Economiser Gas Exit Oxygen % vol 3.41 154 146 APH2 Exit gas temperature °C 194.3 196.2 195.7 Final Gas temperature °C 138.2 141.8 142.0

Outside Ambient Temperature °C 11.8 17.2 15.3 Air cooled condenser Vacuum bar.a 0.085 0.111 1095

Flue Gas Oxygen % vol 4.68 4.70 4.79 Flue Gas Moisture % vol 12.32 12.06 14.26

Lime Consumption kg/h 22.6 614 616

Fly Ash tph 0.276 1233 1302 Fly Ash Dry Matter % 98.8 918 918 Fly ash / kg fuel dry/dry 0.0099 0.0099 0.0125

Total Ash tph 1.828 1.679 1.851 Total Ash kg/kgfuel 0.0766 0.0724 0.0779

Dry Fly Ash Fraction % 14.9 13.7 16.1 Dry Bottom Ash Fraction % 85.1 813 819

Loss on Ignition Fly Ash % 0.7 0.4 0.9 Loss on Ignition Bottom Ash % 4.7 6.2 4.5

Unburned Energy in Fly ash MWth 0.014 1007 1020 Bottom Ash MWth 0.548 0.674 1536 Unburned CO in Flue Gas MWth 0.062 1055 1036 Total Unburned Loss MWth 0.625 0.736 1580

Overall Unburned Loss % 0.53 162 149

Combustion Efficiency % 99.47 99.38 9151

45 7.4 Comments

The trial burn generated sufficient data and information to allow Miscanthus to be compared with cereal straw as an alternative fuel. The periods before and after Miscanthus firing can be used for direct comparison. The key items for comparison are:

• Steam flow rate and steam temperature • Overall plant cycle efficiency • Combustion Efficiency, and • Plant running load

In all aspects the trial showed virtually no difference between cereal straw and mixed miscanthus and cereal straws before, during or after mixed straw firing. A very small increase in parasitic load (from 2.60 to 2.63MW) was observed with the mixed fuel, which slightly lowered the export value during this period. If Miscanthus only had been fired one could expect this 30kW difference to have doubled, however this is still well within normal plant running load variations.

No immediate adjustments or improvements to operation need to be made when firing up to 50% miscanthus and all cereal straw set points can remain in place.

All operating data was easily trended and retrieved and the relaxed manner with which the operator’s handled the trial was a good indication of how well the trial had performed.

46 8.0 Plant Performance

8.1 Energy Balance

To assess plant performance an energy balance was undertaken for each of three periods of the trial, this included the initial cereal straw firing prior to mixed fuel firing, followed by the mixed fuel period of four hours, concluding with the final period when the plant was returned to conventional cereal straw firing. Refer to Appendix 7 for energy balance details.

It is necessary to undertake an energy balance to establish not only to establish the combustion and cycle efficiencies of the plant but also to determine where the fuel energy is used and to verify the energy losses. It is a fundamental part of DIN 1942 and provides useful information to allow quantified adjustments and improvements to be made to plant performance.

8.2 Plant Emissions

EPR Ely is authorised to operate under IPC consent from the Environment Agency. The chimneystack is 46.7 metres high and was designed to British Standard 4076 (1989). The stack design was optimised to provide an efflux velocity in excess of 15 m/s over the normal operating regimes of the boiler. The emissions from the stack are monitored and data logged at the stack and reported to the control room. Additionally this emission data is sent directly to the Environment Agency and East Cambridgeshire District Council by a modem link.

The plant was designed and commissioned to burn cereal straw and one would expect the best emission test values with this fuel. Other straw types would be expected to have higher emission levels.

All emission levels are measured at actual conditions and corrected automatically to reference conditions for compliance purposes. Reference conditions are: 11% oxygen in the dry flue gas, 0°C and 101.3 kPa.

Table 8.2 Emission Test Results

Cereal Straw Mixed Cereal Cereal Straw Emission Units IPC Limits Start & Miscanthus End Particulates mg/Nm3 110 19.0 112 25

SO2 159.7 146.3 2110 300 CO 112.1 100.0 612 250

NO 49.1 715 811 —

NO2 3.4 3.3 3.2 —

NOx (as NO2) 70.3 99.4 116.5 300 HCl 118 24.4 215 30 Dioxins ng/m3 ND ND ND 0.5

Lime Consumption kg/h 22.6 614 616 ---

47 8.2.1 Carbon Monoxide

The level of carbon monoxide achieved was well below the limit for all three periods and perfectly acceptable. This data reflects the fact that the mixed fuel did not require any major adjustments to plant air settings with furnace performance similar to cereal straw alone.

8.2.2 Nitrous Oxides

Nitrous Oxides are determined by the addition of separately measured NO and NO2 components. All values measured are around a third of the limit.

8.2.3 Oxides of Sulphur (SO2)

The fly ash from straw contains reasonably high levels of calcium and potassium, which are very reactive metals and used to capture most of the sulphur (and chloride) in the fuel. This takes place at different temperature points within the furnace, boiler and economiser sections of the steam generating plant. To ensure compliance the remainder is captured in the GSA with the addition of dry lime (Ca(OH)2) and filtered out of the flue gas as solid matter by the high efficiency fabric filter, downstream of the GSA. With a fuel that contains lower levels of reactive metals (calcium, sodium, magnesium and potassium generally), then higher quantities of lime would be required to absorb the sulphur.

The flue gas monitoring system records both SO2 and HCL andthe signals are fed back to the lime dosing equipment to regulate the quantity of lime addition for the for the highest level of either SO2 or HCl.

Results show that Miscanthus and cereal straws require similar levels of lime addition to meet the acid gas limits.

The SO2 emissions on all periods were significantly lower than the limits highlighting a good ability for sulphur retention from both straw types, despite an initial surge in emissions at the start of Miscanthus combustion.

8.2.4 Hydrogen Chloride (HCl)

HCl is not as easy to capture in the higher temperature regions of the steam generating plant as is the case with SO2. However, in the GSA and bag filter, where the flue gas temperature is lowest, the opposite is true. HCL is easily captured in the ash at these lower temperatures and with a modest amount of lime addition up to 90% can be collected.

HCL is collected in the fly ash by the filter in the same manner as SO2.

The results are sufficiently below the set limits (around 2/3 rds) and again show the ability of each straw ash type to retain acid gas components

48 Table 8.2.1 SO2 &HCl Emissions

Units Cereal Straw Mixed Cereal Cereal Straw start & Miscanthus end

Fly ash kg/h 276 233 302 Lime addition kg/h 22.6 65.4 69.6

SO2 Emission mg/m3 159.7 146.3 215.0 HCl Emission mg/m3 18.8 24.4 20.5

8.2.5 Particulates (Dust)

Particulate emission levels can be quite variable and dependant upon the amount of lime addition, degree of recirculation of fly ash, whether the bags have been cleaned or about to be cleaned and is also dependant upon gas volumetric flow, which affects the velocity through the bag.

The results show high levels of particulate emissions for all three periods, this was not a problem with the fuels fired but unfortunately a need to replace the filter bags, which were at the end of their three-year life. New bags, which have since been confirmed, would give the more normal emission level of 1 to 4 mg/Nm3.

Table 8.2.2 Particulate Emissions

Units Cereal Straw Mixed Cereal Cereal Straw start & Miscanthus end Gas Flow tph 189.1 189.4 189.0 Fly ash kg/h 276 233 302 Lime addition kg/h 22.6 614 616 Emission mg/m3 110 19.0 112

8.2.6 Dioxins and Furans

Trace levels of Dioxins and Furans are found in the chimney gas, the bottom ash and fly ash. In the chimney gas the levels observed are a fraction of the authorised limit and in the solid ashes are no more than found in the surrounding soil. Dioxins and Furans (usually referred to as dioxins) are a family of chemicals (containing around 140 different components) based on the tri-cyclic molecule benzo-p-dioxin, which has two benzene rings, linked by two oxygen atoms and have had some or all of the hydrogen on the benzene rings replaced by chlorine.

Dioxins are usually associated with the incomplete combustion of material containing chlorine and as such are commonly associated with the ash from combustion processes, but can be found in small traces in soils. To date only traces have been found in the previous studies of the ashes and flue gases at levels well below the emission limits, as part of the routine power station monitoring

49 Due to time and cost constraints a more detailed examination of Dioxin concentration levels at this power station was not carried out. The cost for undertaking dioxin tests on the flue gas and ashes for three different fuels would have been around £10,000.

Dioxins are usually associated with aspects of poor combustion and these can also be indicated by high levels of CO, several times the limit and by random testing for organic hydro carbons. To ensure dioxins are adequately destroyed the furnace temperature is maintained above 850°C for more than two seconds and the flue gases are quickly cooled between the temperature range 400 and 200°C to prevent any reforming. Control on the 850°C is by the use of natural gas, which always ensures this temperature regardless of straw moisture and furnace conditions.

8.2.7 Emission Control Techniques

Emissions from a biomass-fuelled boiler can be controlled by a variety of methods. The control systems needed depend mainly on the composition of the feedstock, variations in moisture content and variations in calorific value. If control is lost this can lead to increased emission problems, predominantly due to incomplete combustion and increased carbon monoxide emissions or excessive temperatures leading to high NOx emissions.

The acidic flue gas from the furnace enters the cleaning plant at the bottom of the GSA reactor where the gas is mixed with dry lime and with re-circulated fly ash that has been collected. The fine lime is evenly distributed with a very large contact surface area and is carried with the flue gas through the GSA allowing a neutralising reaction to occur.

The removal of the acidic components of the flue gas is a result of the following chemical reactions:

2 HCl + Ca (OH) 2 => CaCh + 2%O SO2 + Ca (OH) 2 + H2O => CaSO3 + 2H2O

The resultant Calcium compounds are particulates and are removed in the fly ash by a fabric filter. The purified flue gas now relieved of both the dust and acid components are released to the atmosphere through the chimneystack well below the emission limits.

Lime is added automatically by means of a screw conveyer system and transfer pipe. The amount to be added is determined by the control system, which measures the HCl and SO2 emissions from the stack.

50 Fig 23 Left: Picture of the bag filter system showing 3 of the 6 compartments. Right: Picture of the lime silo and dosing system beside the Gas Suspension Absorber

The plant uses a Fabriclean™ Filter system. This comprises of six cleaning compartments arranged in parallel, which receive gases from a common inlet manifold. The flue gases from the furnace are drawn through the filter compartments under the influence of the Induced Draught fan.

The collected dust is dislodged automatically from the filter bags by short pulses of compressed air injected into each row of bags. The cleaning cycle is initiated by differential pressure measurements when a predetermined level of resistance is obtained over the filter.

The high efficiency fabric filter removes +99.95% of all particles from the flue gas after the GSA to fulfil the emission guarantees on particulates.

NOx levels can be controlled and maintained below emission limits by the use of special equipment such as SCR or SNCR (selective catalytic reduction and selective non-catalytic reduction). These processes use ammonia or urea injected into the furnace and boiler sections to capture NOx from the flue gas. This equipment is very expensive in both capital and running cost and not available at the Ely power station. Instead, at Ely, the traditional method for NOx reduction has been adopted whereby air is entered into the furnace at different heights (staged combustion) with control on furnace temperature (in the range 850° to 1050°) throughout.

51 CO levels are maintained in a similar way by adding air at different stages to even outthe combustion rate in the furnace, without creating excessively high or excessively low temperatures. High temperatures lead to an increase in NOx but a reduction in CO whereas low temperatures lead to a reduction in NOx but an increase in CO. It is very important therefore that good control of the straw bale moisture content is maintained and the reason why a maximum limit of 26% moisture is placed on bales during loading in the straw barn. High moisture can quench furnace temperatures and lead to excessive CO emissions.

8.2.8 Comments and Conclusions

Supply of Miscanthus to the furnace occurred at the same time as a dip in power generation and a rise in furnace oxygen level, which is normally associated with a short period of poor combustion. This was followed by a surge in emission levels that still met hourly limits but caused a short-term excursion. The plant took an hour or so to recover back to more normal conditions. This was a potential problem envisaged before the test and one of the reasons the amount of Miscanthus was limited to around 50% of solid fuel firing.

§ CL 8 1 LD if) 8 (3

Time Fig 24 Power Output & Oxygen Level ■ oxygen ■ Power

52 r 45

40

35

30 25 I

1 20

15 O 10

5

0 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00 Time

Fig 25 Straw Emissions Dust ■ S02 -hr- CO ■NOx HC1 ■Power MW

The emission test results, table 8.2, show emissions for the start on cereal straw, the period of mixed fuel firing and for cereal straw only at the end of the test to see if there was any ‘follow-on’ problems. All three periods were well below statutory limits.

In conclusion baled Miscanthus straw has sufficiently proven itself to burn efficiently, meet IPC limits and plant output requirements.

8.3 Ash Details

Ash samples were collected from the conveying lines during each test period and analysed for their combustible content, to provide data for energy balance purposes.

Table 8.3 Ash Analyses

Cereal - Start Cereal + Miscanthus Cerea - End Bottom Fly Ash Bottom Fly Ash Bottom Fly Ash Ash Ash Ash

Dry Ash Fraction % 85 1 14.9 86 3 13.7 73 9 16.1 Loss on Ignition % 4.7 0.7 6.2 0.4 4.5 0.9 Unbumed Loss % 0.46 0.01 0.57 0.01 0.45 0.01

53 A full elemental ash analysis was not undertaken for this trial since no particular problems were encountered with combustion during any stage of the trial. The proximate details given in table 8.3 are sufficient for energy balance purposes and to compare performance at each stage.

A little more bottom ash was produced with Miscanthus with marginally higher unburned loss, as indicated by the loss on ignition value. There is no particular reason for this except that Miscanthus is probably denser than cereal straw with less tendency to fly. However the results are so close and well within the normally accepted range that adjustments to plant are not required. If the plant was operated on 100% Miscanthus then this small figure may increase to double the difference but even this would not be considered a problem.

54 9.0 Financial Implications

9.1 Straw supply

The cost of baled straw as a fuel is dependant upon a number of factors such as calorific value of straw type, moisture content, soil inclusions, transport distance, cost of baling and storage and seasonality effects, which may reduce the available quantity of purchased straw to the power station. The power station operator requires a steady supply of suitable straw throughout the year, at a regular known price and does not want to be unduly affected by these variations.

To smooth out the variations in delivery and delivered price Anglian Straw provide the buffer between the farmer and haulier on one hand and the power station demands on the other. They look after the whole of the supply and storage logistics and coordination requirements, ensuring and maintaining a steady, reliable and suitable supply of straw.

9.2 The Price of Straw

The cost of straw to the power station is currently based on the use of cereal straw at an annual average moisture content of 16 % by weight. The following table (table 9.1) details the current price of cereal straw and the price for baled Miscanthus, as determined by the combustion trial, and corrected to the same basis for moisture and transport distance.

The price of baled Miscanthus is much the same as for cereal straw at £15.50 per bale. This is not surprising since many of the suppliers of Miscanthus will also provide much of the cereal straw to the power station. When compared as a price per tonne Miscanthus is not as favourable as cereal straw because the cost of baling will be higher. Yield rates, however, are higher for Miscanthus at around 7tonne per hectare compared with cereal straw at 5 tonne per hectare.

Table 9.1 includes a loss factor. This is an allowance for material loss due to degradation in the field and inclement weather. Exceptional rainfall, fire and alternative supply requirements incur a cost additional to the totals given in the table.

All costs quoted in table 9.1 are typical. Actual values will vary from farm to farm according to the arrangements undertaken with the farmer, the level of split responsibility, loading requirements, netting requirements, delivery distances, provision of all weather sites and time of year.

If Miscanthus can be mown in the field to slightly shorter lengths with stronger twine used, then the ability to pack each bale of Miscanthus to a higher density would help reduce transport costs by up to £1.00 per bale. Current transport vehicles are limited to a gross tare weight that cannot be exceeded, this restriction would limit the maximum bale weight to 750kg and not the 850 kg that the power station was designed to take.

55 Table 9.1 The Cost of Straw

Cereal Straw Miscanthus Miscanthus Baled Tested Tested Denser £/bale £/tonne £/bale £/tonne £/bale £/tonne

Nominal Bale Weight kg/bale 503 539 750 Nominal Yield tonne/ha 5.0 7.0 7.0

Nominal Payment at Farm 1.50 298 160 2.98 223 2.98 Mowing 1.50 298 160 2.98 2.24 2.98 Baling 500 994 6 50 12 06 7.50 10.00 Chase to stack 100 1.99 1.00 1.85 1.00 1.33 Load & Deliver 4.90 974 490 9.10 400 5.33 Loss Factor 1.10 2.19 0.70 1.30 0.70 0.93 Overheads & Costs 050 099 050 093 050 0.67

Total Cost 1550 3081 1680 3120 18.17 24.22

Cost £ per GJ (16 % Moisture) 2.29 2.20 1.71

Variations with Moisture

The annual average moisture of 16% by weight would command a price of 100% of the fuel cost, as given in table 9.1.

110 105 100 95 £ 90 | 85 U 80 75 70 10 12 14 16 18 20 22 24 26 28 30

Moisture Content %

Fig 26 Straw Cost Variations with Moisture Content

56 Maximum Acceptable Moisture per bale is 26 % Maximum Acceptable Moisture per load is 23.5 %

The reason for limiting the moisture content is that at high moisture the calorific value is reduced and to maintain output more fuel has to be fired. The limiting factors on this are the maximum capacity of the burner, shredders and screw feeders andthe furnace volume, which is fixed, and gas residence times would therefore be reduced. The limiting condition in this case is for a minimum of 2 seconds residence time. There is also the potential for blocking and fouling of plant components, such as the bale shredders

£ ©e o. E s tzi ©= U % 5

Moisture Content %

Fig 27 Variation in Straw Consumption with Moisture Content

The power station currently consumes around 200,000 tonnes of straw at an average 16% moisture for 8,000 operating hours per year. The total cost of fuel is £6.2 million per year (year 2002). Fig. 26 shows how the quantity of wet straw required, to maintain power station output, changes with moisture and Fig. 27, how the price paid reflects this to ensure that, no matter what moisture straw is delivered at, the power station always pays £6.2 million. This amount is escalated each year with the retail price index.

As the price varies with moisture at the power station, so does the price paid to the farmer. This variation is passed directly and in the same way, but after transport and handling charges. It is clear, therefore, that if the farmer can harvest and store his straw and accurately measure the moisture, giving an improved tonnage at lower moisture, then he can maximise his income. Equally if less is delivered, or is wetter, then less income can be raised.

57 10.0 Comments and Conclusions

10.1 Agronomy

Planting in 1999 took place under less than ideal conditions and plant establishment was poor; replanting the following spring did not improve plant population very much. The plant population in 2000 remained unchanged for the rest of the project. Plants grew well and stem density increased each year. Most shoots emerged in spring, which resulted in a fairly uniform shoot size on individual plants. Stem height reached 2.4m in 2002. This is the measurement to the last leaf collar therefore actual height is about 50cm taller.

Lessons learnt at Witcham about how to plant Miscanthus rhizomes have been useful in developing planting strategies. Although the number of established plants was low the population has been maintained throughout the project. Plants have grown well and development has been comparable to plants grown elsewhere in experimental plots. Stems per plant are similar to values reported elsewhere. Harvesting in 2002 created extensive wheel marks across the field that could be clearly seen later in the year. However plant growth afterwards was not affected.

Monitoring growth has shown that most shoots emerge in the spring and early summer except in the planting year. The contribution to stem density from late season shoots was negligible. Late emerging shoots may die possibly from shading in the older crop. This growth characteristic means that a greater uniformity of stem size is present at harvest.

Some new shoots for the next season were evident by late summer and if they grow too much before the winter they would be vulnerable to frost damage. However the majority of stems arise from buds deeper in the soil and these have been unaffected by frost or wheel damage andthis could be the reason why wheeling did not affect growth.

The fact that water logging did not kill plants is a very positive finding but soil water logging is detrimental to harvesting operations and its timing. Water logging did affect stem growth and it was evident that differences between plots were related to the length of time that plants were subject to winter water logging. In 2001 and 2002, stem height was shorter at the end of the summer on the plot not affected by water logging. This suggests that soil water reserves were better on the other plots and supported better growth. But it might also be a topographical effect with water draining to the area from the drier bank on which plot 1 is situated.

Pre-planting strategies for weed control could not be carried out because of the brief period available for planting after the wheat had been removed and this probably contributed to the level of weed infestation. Also weed suppression by the crop was not very effective because of the low plant density. The result demonstrates the value of good weed control prior to planting and the importance of a high plant density and good spatial distribution.

There have been no pest or disease problems andvery little damage by animals and the field has supported a range of birds and animals demonstrating the value of the to bio-diversity.

58 10.2 Combustion Trial

Overall, both cereal and mixed cereal and Miscanthus fuels appeared to perform in a similar manner with no significant handling, chopping, combustion or ash handling problems encountered.

The project has shown the feasibility of using Miscanthus up to 50% solid fuel ratio when mixed with conventional cereal straw without any significant impact in environmental emissions, energy efficiency or ash handling.

Use of Miscanthus, although a more expensive fuel, still offers some advantages financially because of its higher calorific value and bale density. This will help reduce the cost per tonne and more importantly the cost per unit energy to the power station.

Miscanthus is a suitable fuel for use in plants similar to Elean, it provides an alternative fuel resource for this existing plant and opens up the potential for further biomass plant development in the UK. The use of this fuel reduces the dependency and risks associated with the use of only one fuel type and allows alternative periods of the year for harvesting, when equipment is not being utilised elsewhere.

Table 10.1 Overall Cost of Straw by weight and Energy Supplied.

Cereal Miscanthus

Load & Deliver Cost £ / tonne 9.74 9.10 £ / GJ 0.72 0.64

Total Cost £ / tonne 30.81 31.20 £ / GJ 2.29 2.20

* Total cost excludes any payment to the farmer, for non-food crops grown on set-aside land

Use of a broader range of fuels could help the sustainability of the overall combustion process by improving the reliability of the fuel supplies. Sufficient fuel quantities would appear to be available within an economic transport distance to ensure the future use of Miscanthus.

10.3 Assessment

A method of assessing Miscanthus was developed prior to the test work and was designed to ensure that any particular impact on operation and performance was clearly observed and reported. Performance against the assessment parameters is shown below.

59 Ease of handling and conveying

Both cereal and Miscanthus, in baled form, handled and conveyed in a similar manner

Ease of chopping

All baled materials chopped successfully although Miscanthus required a small increase in torque setting, indicating that it was slightly tougher to chop.

Ease of entry into combustion chamber

No particular problems were encountered with either baled type.

Furnace temperature profile

A similar profile was encountered with cereal straw andthe mixed fuel. Miscanthus tended to burn more intensively at the beginning of the trial, which allied with a drop in output just previously, caused a short-term emissions excursion.

Steam and electrical production rate

Steady steam rates of around 142tph were achieved throughout. A very small increase in parasitic load (from 2.60 to 2.63MW) was observed, however, with the mixed fuel, which slightly lowered the export value during this period.

Plant chimney emissions

With the exception of the short-term excursion at the start of mixed fuel firing, all plant chimney emissions were below the emission limits on an hourly basis. Performance throughout the test showed very little difference when burning Miscanthus and is very encouraging.

Ash collection and removal

No particular problems were encountered on either bottom ash or fly ash with either cereal or mixed cereal and Miscanthus ashes. Experience with other straw types, particularly Oil Seed Rape, has shown that the bottom ash may tend to float in the quench bath, making ash extraction more difficult. This was not encountered with Miscanthus.

Currently the fly ash is pneumatically conveyed to a fly ash silo where it is stored prior to removal to land fill. The wet bottom ash, containing no lime addition, is mechanically transported to a large hopper prior to sale as a building aggregate material. The ash quality and consistency did not vary on either discharge route and removal from site posed no problems.

Operating stability

The mixed fuel took an hour to settle down and for emissions to stabilise. Once settled the operation of the plant became relatively stable and, although a variety of different moistures was

60 not encountered, it would appear that either type could have operated for long periods without operator intervention. With cereal straw the ratio of natural gas fired to solid fuel can be adjusted to provide prolonged stability in the event of differing fuel moisture, provided the maximum moisture limit, at fuel reception, of 26% by weight is adhered to. This should also be a valid operation for high moisture Miscanthus.

Sustainability & Availability

Due to the limited nature of the test work, covering a one-day trial only, the question of sustainability of combustion is more difficult to establish. Given the very similar results and performance between the two fuels, one could expect Miscanthus bales to provide long-term results similar to wheat. There appears to be no valid reason why Miscanthus should not become a regular contract fuel.

Plant availability is currently around 90%, having been proven over a two-year period. New fuels usually create new problems and any other type of baled straw would require at least 3months continued use before it’s impact, if any, on the availability of the plant could be truly assessed. From the results of these trials it would appear that Miscanthus would have little impact on the long-term availability.

61 REFERENCES

Brown R A (1978). A difference in N use efficiency in C3 and C4 plants and its implication in adaptation and evolution. Crop Science.

Christian D G & A B Riche. (1999). Establishing fuel specifications of non-wood biomass crops. Department of Energy Contract Report B/U1/00612/REP. Energy Technology Support Unit (ETSU), Harwell, Oxford, UK.

Christian D G, A R Riche & N E Yates MC. (1999). Monitoring growth and yield of crops grown as biofuels. Department of Energy Contract Report B/W2/00548/11/REP. Energy Technology Support Unit (ETSU), Harwell, Oxford, UK.

Hodkinson T R , Renvoize S A & Chase M W. (1997) Systematics of miscanthus. In Bullard M J; Ellis R G; Heath M C; Knight J D; Lainsbury M A & Parker S R (eds), Biomass and energy crops. Aspects of Applied Biology, 1997.

Rutherford & MC Heath. (1992). The potential of miscanthus as a fuel crop. Department of Energy Contract Report B 1354. Energy Technology Support Unit (ETSU), Harwell, Oxford, UK.

FEC Ltd (1988) Straw Firing of Industrial Boilers. Department of Energy Contract Report ETSUB 1158. . Energy Technology Support Unit (ETSU), Harwell, Oxford, UK.

Garstang J.R. (1994). The Analysis of Straw. ADAS Cambridge. Department of Energy Contract Report B/M3/00388/39/REP. Energy Technology Support Unit (ETSU), Harwell, Oxford, UK.

ETSU B-W2-00619-REP Development of Generic Solutions for Biomass Storage and Transport.

ETSU B 1242 Straw Ash Characteristics.

ETSU B/M5/00533/16 The Fast Pyrolysis Of Oil Seed Rape

ETSU B/M4/00487/01 Energy and Carbon Analysis of Using Straw As A Fuel

ETSU B/M3/00388/39 The Analysis of Straw

62 APPENDICES

A1 Layout of Trial Plot at Witcham, Mepal

A2 General Grower Guidelines

A3 General Comparison of Fuels

A4 Normal Operating Details of Ely Power Station

A5 Plant Instrumentation

A6 Test Procedures

A7 Overall Steam Cycles and Efficiency

A8 Plant Emissions

A9 Details of Sub-Contractors

A10 Key Staff

63 Ruad APPENDIX

O n

1

Layout of Trial Plot at Witcham, Mepal APPENDIX 2

GROWER GUIDELINES

Management plan for EPRL site at Witcham

This plan outlines a proposed course of action to produce a commercial quality stand of Miscanthus as a demonstration facility at the Witcham site, Cambridgeshire. The stand shall have a minimum plant population of one plant per m2, as agreed, planned, (and confirmed by independent assessment of emergence) for May.

The proposed actions have been divided into two areas, remedial work on the current stand, and maintenance work following this action.

Remedial Work

This work is to be carried out once above ground growth has become dormant, it is proposed this would occur alter November, but a decision will be made based on grown during this growing season. • Harvest of above ground cane, to be baled and stored in the field for collection • Herbicide application to remove residual weed populations.

• Cultivation of the demonstration area to re-establish current stands in homogenous manner, the area will then be rolled to ensure soil-rhizome contact Additional rhizomes will be established if appropriate.

Maintenance work

• Agronomic inputs of fertilisers and agrochemicals will be determined by visits to the site, and presented in a detailed programme giving required compounds, rates and time of application.

• Crop diary maintained for all inputs into the crop, to be supplied if requested when demonstration facility is used.

• Access to BICAL telephone help line and technical staff for advice on me maintenance of the site to commercial standards,

65 APPENDIX 3

GENERAL COMPARISON OF FUELS

Fuel Type Typical Straw Miscanthus Coal Wheat & Barley Anticipated Daw Mill

Proximate Analysis, as received

Moisture % range 11.8-22.4 12-25 % Ave 16.2 16.0 7.2

Ash % range 3.2-8.2 As Straw % Ave 5.5 5.5 6.2

Volatile Matter % range 57.2-69.7 As Straw % Ave 63.5 62.5 34.1

Fixed Carbon % range 14.8-16.0 As Straw % Ave 15.2 16.0 50.5

Ultimate Analysis, dry basis Range Range Average

Carbon % by weight 40.9-48 43-48 68.7 Hydrogen % by weight 5.3-6.4 5.6-6.2 4.5 Nitrogen % by weight 0.3-0.9 0.2-0.6 1.1 Chloride % by weight 0.1-0.6 0.2-0.9 N.D. Sulphur % by weight 0.2-0.4 0.02-0.40 1.5 Oxygen (by difference) % by weight 36.9-39.1 38-42 8.8

GCV dry basis kJ/kg 17,840-18,600 18,000-20,000 31,057 GCV dry ash free kJ/kg 19,260-19,600 19,500-20,500 33,110

Ash Fusion Temperatures

Initial Deformation Temp °C 800-1400 1000-1150 1225 Hemisphere Temp °C 930-1430 1200-1350 1265 Fluid Temp °C 1100-1440 1300+ 1320

Note: Ash content, due to soil inclusions, may vary considerably according to ground conditions at time of harvesting.

66 APPENDIX 4

NORMAL OPERATING DETAILS OF ELY POWER STATION

Name: Elean Power Station

Location: Sutton near Ely, Cambridge

Site Size: approximately 4.5 ha (10 acres)

Technology: FLS miljo Vibrating Grate / Whole bale burner

Main Furnace Temperature: 850°C

Number of Furnace Lines: 4 feed lines to separate burners on a single furnace

Plant Capacity: 200,000 tonnes of straw per year plus 10% Natural Gas by energy Input

Net Electricity Output: 36 MWe Normal, 38 MWe Winter Condition

Net Thermal Input 103 MW thermal, Normal

Overall Cycle Efficiency 35.0%

Steam Turbine: 2 stage condensing

Steam Conditions: 92 bar/540°C

Cooling: Air-cooled condenser

Stack Height: 43.5m

Plant Residue: Potash and phosphate rich ash

Emissions: IPC ref. S2 1.05 Limits Typical

Particulates < 25 mg/m3 < 4 mg/m3 SOx <300 mg/m3 60 mg/m3 NOx <300 mg/m3 250 mg/m3 HCL < 30 mg/m3 18 mg/m3 CO < 250 mg/m3 120 mg/m3

67 APPENDIX 5

PLANT INSTRUMENTATION

Flue Gas

To assist in the control of plant processes and to monitor the emissions to air, on line instruments monitor, display and record all important process parameters.

All instruments are calibrated on a regular basis using a reference gas at a fixed level or by a physical test such as an isokinetic sample, in the case of particulate. Full-scale accuracy is less than 2% of the measurement range.

The monitoring equipment is kept within an air-conditioned cabinet mounted within a steel container situated at the bottom of the stack. Three types of analyser make up the equipment. A GP 2000 H particulate monitor (Pillard Opastop), an Oxygen monitor, Oxitec 5000 (Enotec) and a Gasnet CX-4000 (Temet), which determines the concentration of CO, HCl, S02, NO, NO2 and water vapour using Fourier Transform Infra-Red analysis. The reference conditions of the measured substances in the gas sampled are 0°C, pressure 101.3kPa, dry gas, at 11% oxygen by volume. Samples of the gas emissions are taken through heated probes from a point 15 metres above ground level within the stack. From the measuring points the gas is brought to the cabinet through a heated sample line. The gas is then automatically measured using the three analysers andthe data gathered transferred to a networked computer to allow for real time monitoring by the plant operators.

Table A5.1 Monitoring and Reporting Instruments for Emissions to Air

Parameter Units Monitoring Instrument Continuous Non Continuous Frequency Range Standard Standard

Particulate mg/m3 Continuous 0 - 50 BS 13010155 BS : 6069pt 4.3 Oxides of Nitrogen mg/m3 Continuous 0 - 1000 NO ISO 10849 BS :150 11564 0 - 50 NO2 Oxides of Sulphur mg/m3 Continuous 0 - 1000 BS6069Pt4.1 BS :15011632 Carbon Monoxide mg/m3 Continuous 0 - 300 and ISO 12039 ISO 12039 0 - 1000 Volatile Organic mg/m3 Periodic 0 - 100 BS : EN12619 Compounds Hydrogen mg/m3 Continuous 0 - 30 and BS : EN1911 Chloride 0 - 100 Flow Nm3/h Continuous 0 - 200,000 Oxygen % vol Continuous 0 - 21 Moisture % vol Continuous 0 - 30

Alarm levels are set well below EPA limits.

68 Internal reports were compiled specifying the following information on plant operation and monitoring: • Hours run

• Emissions (corrected to reference conditions)

Flue Gas Flow (dry basis) Flue Gas Oxygen (dry basis) Flue Gas Moisture

Particulates Retrieved DCS archives CO emissions Retrieved DCS archives SOx emissions Retrieved DCS archives HCl emissions Retrieved DCS archives NOx emissions Retrieved DCS archives

69 APPENDIX 6

TEST PROCEDURES

The combustion test was to be undertaken in general accordance with DIN 1942, which requires a minimum period of three hours continuous duration.

All trials were to be carried out at MCR conditions and continued for a period of 4 hours until the baled Miscanthus ran out, the plant was then returned to full cereal straw firing.

Data logging throughout each trial was to be undertaken on an hourly average basis and manual logging of data undertaken on the hour.

Sampling and Recording Requirements

• Plant Data - to be continuously recorded by the plant plc system during the test, utilising the pre-calibrated in-house instruments and printed out at the end.

• Fuel - sampled on a regular basis during the test and aggregated (independently), for the analysis period.

• Ash Samples - taken and aggregated in the same manner.

• Emissions Data - The pre-calibrated continuous monitoring equipment installed for recording emissions to EA standards were to be employed with test data trended on the plant plc system.

Recorded Data

Trended and manually recorded data includes:

Steam Flow tph Pressure bar Temperature oC

Feed water Flow tph Pressure bar Temperature oC

Blow down rate (if applicable) % of steam flow

Total Air Flow m3/h Air Temperature oC Air Humidity kg/kg dry air (or rh) Fuel tonnages (from crane) tonnes Moisture %wt Economiser Gas Exit Temperature oC

70 Economiser Gas Exit Oxygen % vol Fly ash collected tonnes Bottom ash collected tonnes Electrical Export Gross MWe Electrical Export Net MWe Plant power load MWe Natural Gas Consumption ft3

Chimney Emissions:

NOx mg/Nm3 at 11% O2 ref SOx HCL CO Particulates

Laboratory Analysis:

Fuel Ultimate Analysis + GCV & NCV Fly Ash Analysis Carbon in ash/loss on ignition Bottom Ash Analysis Carbon in ash/loss on ignition

General:

Monitoring and recording by general observation was also undertaken during combustion for identification of any variations to normal plant operation that could impact on plant efficiency or emission levels.

Natural Gas Calorific values were to be obtained from the supplier to establish the correct energy input.

71 APPENDIX 7

OVERALL STEAM CYCLE & PLANT EFFICIENCY

• Boiler & Overall System Diagram For the Mixed Cereal & Miscanthus Trial Period

• Summary of Overall Energy Balance for all three test periods

72 All values are in kW

Fig 28 Overall System Diagram Mixed Miscanthus and Cereal Straw

73 Summary of Overall Energy Balance

Cereal Start Mixed Fuel Cereal End Heat Input kW

Heat from straw kW 106,648 106,471 106,141 Heat from Natural Gas kW 6,835 6,886 7,316 Heat in Preheated Air kW 4,712 4,822 4,764 Total heat to Input kW 118,195 118,179 118,221

Boiler Duty kW 102,842 102,635 102,631

kW % kW % kW % Dry Gas Loss Moisture Loss " Flue Gas Loss % 9,829 8.316 9,960 8.428 9,909 8.382 Humidity Loss Solids Loss % 122 0.104 113.8 0.096 121 0.102 Unburned Loss 625 0.529 736 0.623 580 0.491 Radiation and Convection Loss 540 0.457 540 0.457 540 0.457 Soot blower Loss % 0 0.000 0 0.000 0 0.000

Total Losses % 11,117 9.405 11,349 9.604 11,150 9.432

Boiler Efficiency Calculated % 90.595 90.396 90.568 (Indirect Method) Boiler Efficiency from Test Averages 90.623 90.542 90.459 (Direct Method) Error in Calculation by direct Method 0.028 0.145 -0.110

Combustion Efficiency % 99.471 99.377 99.509

Gross Power Generated MW 39,580 39,150 39,600 In - House Power MW 2,600 2,625 2,600 Net Export Level MW 36,980 36,525 37,000

Overall Cycle Efficiency 32.59 32.22 32.61

Straw Specific Fuel Consumption 0.753 0.740 0.749

74 APPENDIX 8

Plant Emissions

• Summary of Plant Emission Levels, in half hour averages

75 Emission Level mg/m3 Fig — ♦ — Cereal 29 Dust Summary

Only S02

of

Plant Mixed

Emission

Cereal CO

Levels,

& Time

76 Miscanthus —

in NOx

half

hourly — *

averages — HC1 Cereal

— Only • — Power

MW

Gross Electrical Power MW APPENDIX 9

DETAILS OF CONTRACTORS

Energy Power Resources Ltd. Energy Power Resources is a leading UK developer of renewable energy projects. It has a proven track record and a diverse portfolio; including chicken litter, straw and wood burning projects. Currently, EPR has two biofuel power stations constructed and in operation with three further schemes at planning approval stage.

Northern Straw Northern Straw is the largest specialist straw baling contractor and trader in the UK, baling approximately 100,000 tpa. The company, formed almost 20 years ago, is based in Goole, East Yorkshire and employs @ 40 staff. Northern Straw’s Managing Director and co-founder is David Johnson a very well known figure in the industry and the President Elect of the UK Hay and Straw Merchants Association. Over the years Northern Straw has undertaken and contributed to a number of research studies on the straw market and its utilisation, including ETSU report B/M4/00487/16/REP

Anglian Straw Ltd. Anglian Straw is a subsidiary of EPR Ely and is the UK’s largest biofuel logistics company. The company specialises in providing ‘just in time’ deliveries of biomass, particularly straw, from farmers and suppliers to end users such as energy producers.

IACR — Rothamsted The Institute of Arable Crops Research (IACR) has three main research laboratories and three research units. The Institute is grant supported by the Biotechnology and Biological Sciences Research Council.

IACR’s scientific objective is the provision of basic information for improvement of yield consistency, quality, production efficiency and competitiveness of major arable crops in sympathy with environmental considerations.

The Institute’s multidisciplinary expertise operates from cellular level to field studies. The staff complement is about 800 with 500 working at Rothamsted.

Annual income is about £27M of which about 40% is derived from non-government sources i.e., industry levy boards andEuropean Commission funds.

Bical Bical was established by a group of West Country farmers in England 1998. Bical offers a practical understanding of establishing and marketing this crop, with its own well qualified technical staff and agronomists. It also employs a team of practical farmer members who visitall new growers and provide a close, practical based advisory service on each and every farm.

77 APPENDIX 10

KEY STAFF

John Hewson: EPR Ely Project Director Qualifications: MSc Energy Engineering BSc Environmental Science

Previous Experience: John was specifically recruited by EPR to deliver the £60m Ely Straw Power Station Project. He was responsible for negotiating the contracts associated with the scheme and managed the project through financial close. He lives in East Anglia and has a long­ term role in the construction and future of EPR. He is currently responsible for the establishment of Anglian Straw, which will become the UK’s largest straw logistic company. Before joining EPR, John worked for AEP, the development arm of Compagnie Generale des Eaux, the world’s largest operator of EFW plants. As Project Manager he spent 6 years developing MSW Waste to Energy and Biomass plants. Prior to this, he spent 10 years working for a leading environmental consultancy group, culminating in the project management of two landmark Refuse Derived Fuel power plants.

Dudley Christian: IACR Project Leader Qualification: BSc

Previous Experience: Dudley is project leader on energy crops research at Rothamsted Experimental Station. He has been conducting research on herbaceous energy crops since 1993. He has participated in the EU funded Miscanthus network and currently in both the EU funded Miscanthus Improvement Programme and the EU Switchgrass Evaluation Project. He has also participated in a number of ETSU funded projects. Prior to these he conducted research on soil cultivation, agronomy of cereals and cover crops, control of volunteer cereals and the dynamics of N uptake in barley. He has a BSc. in agriculture and HND in agricultural engineering.

Robert Newman: EPR Ltd., Technical Manager Qualifications: BSc Mech Engineering

Previous Experience: Robert has over 30 years experience in engineering, with the last 20 years being directly involved in energy and design. As a senior engineer he has specific expertise in combustion, fuels, fuel handling, control systems, the efficient use of energy and has designed and built energy systems world wide.

Amber Jenkins: EPR Ltd., Energy Development Executive Qualifications: BSc Environmental Geology

Previous Experience: Amber has sound experience in environmental engineering, spending the last 5 years directly involved in renewable energy development, particularly in biomass

78 applications on a variety of scales. Amber is currently completing her MSc in Renewable Energy Technology with CREST at Loughborough University and is specialising in biomass fuels and technology. Amber’s role in EPRL covers areas such as plant procurement, project development, and the preparation of IPPC applications and Environmental Impact Assessments. She has managed several grant-aided biomass (energy crop) projects and is part of the biomass development team.

Nigel Viney: Director European Renewables Ltd. Project Manager Qualifications: H.N.D Agriculture

Previous Experience: Nigel has been involved in agricultural merchandising since leaving Shuttleworth Agricultural College. He gained a wide experience dealing with all aspects of arable farming and trading, whilst working for Sidney C. Banks plc. Five years ago, Nigel progressed to become Arable Manager for Banks Agriculture. During this period he was responsible for the overall management of that company’s involvement in both wood and straw firing of power stations.

Nigel is a Director of European Biofuels Ltd. and European Renewables Ltd.

Andy Middleton:

As Operations Manager for Anglian Straw Ltd., Andy is responsible for all the day-to-day operation of ASL’s straw gathering activities. These responsibilities include the organisation of bringing all contracted and special deliveries of baled straw to site; beginning with the crop in the field and culminating in site storage.

79