MISCANTHUS Practical Aspects Of Biofuel Development INTERIM REPORT ETSU B/W2/00618/REP DTI/Pub URN 02/1512 Contractor Energy Power Resources Ltd Prepared by Amber Jenkins & Robert Newman Subcontractors Bical Ltd Northern 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. _____ First Published March 2002 © Crown Copyright 2002 EXECUTIVE SUMMARY Project Description To plant and establish an energy crop of Miscanthus, monitor and record its growth then harvest the fuel, bale it and deliver to a suitable power station for combustion trials. Thereby demonstrating the commercial potential and suitability of Miscanthus as a biofuel. The project was started in April 1999, with a duration of 48 months and is due to be completed in May 2003. This document summarises the progress of work to date, observations and recommendations for the second half of the project. Background The government has set its objective for a 10% contribution from renewable energy 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 36MW straw fired Elean Power Station, at Sutton, near Ely, EPR could offer Miscanthus growers the opportunity of a long-term fuel supply contract if Miscanthus could be shown to be a suitable replacement or supplement straw, without adverse restrictions on the operation of the power plant. Miscanthus is one of the most researched and most advanced, non-straw, biofuel crop. 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 an efficient converter of solar radiation to biomass energy under the right conditions. To promote the use of Miscanthus, it is essential that its production, storage, handling and combustion be demonstrated on a commercial scale. This project aims 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 and Results to date Work on this project to date has concentrated on two main areas: • Modification of EPR's Elean plant to accept and use miscanthus as a fuel • Planting, growth monitoring and future harvesting of the miscanthus fuel. ii Plant Modifications Modifications were required in the design of the Elean plant to enable the power station to accept miscanthus as a fuel. Two options for introducing miscanthus into the facility were identified and evaluated. Each option was designed and costed. Both options were investigated thoroughly, with the advantages and disadvantages of each being considered. 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 implications. Option 1 - Chopped Miscanthus Option 1 was to modify the plant to accept chopped miscanthus. Provision would be made for a covered loading area with a large storage pit and a purpose designed conveying system delivering metered volumes onto the straw feed lines and into the combustion system. This option however has its limitations at Elean in that the quantity of chopped fuel that could be used would be limited to a maximum of 25% of the total at any time due to the 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. However, obtaining even combustion rates across the furnace could not be guaranteed. The potential for slagging and fouling was identified which could lead to localised high temperature zones which could prove detrimental to plant performance and availability. The capital cost to provide this system in its entirety was prohibitive as it would be close to the original total budget for this project of £270k and furthermore a change to the planning permission would be required due to the need for a revised building layout. Option 2 - Baled Miscanthus The second option considered was to introduce 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 the denser 850kg Miscanthus bales. This design was inherently integrated with the existing plant layout and did not therefore require any planning revisions. The capital cost to achieve this modification was £190k. iii 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. Evaluation of the miscanthus combustion trial was considered to be much easier with direct comparison being made between baled straw and baled miscanthus. Perhaps the most important consideration in the selection of the feed system for miscanthus was that of finance. At the time this was considered EPR could not obtain approval for the provision of an extra £1.2 million in plant costs, as the market for chopped miscanthus was clearly not established and still isn ’t. In light of these considerations it was decided that the project would go ahead with the upgraded bale handling system. However, the designs for the chopped miscanthus handling systems have been retained and should the market for chopped miscanthus develop could be reconsidered for future plants. Modifications for the receipt, transport and introduction of baled miscanthus into the combustion process with modifications to the crane and feed system, to allow for denser, heavier Hesston bales, were implemented during the last part of the Power Station construction. Production of miscanthus. A suitable site for the trial plot was identified close to the Elean Power Station. The field is 12ha in total and had been in continuous wheat production for a number of years. Two hectares of the field were set aside for the Miscanthus trial. The soil type is a clay loam, from which the usual spectrum of agricultural broad-leaved weeds, couch grass and some wild oats was expected. The original plan was to establish the 2ha plot for miscanthus, grow for 2 years, and then use the rhizomes to plant a larger area to give sufficient biomass for a combustion trial. Conditions at the time of planting were poor. It was late in the season with dry weather and followed a recent wheat crop. In August 1999 planting commenced at a density of about 2 to 2.5 rhizomes/m2. By November 1999 monitoring of the trial plot was underway. At this time, some plants showed reasonable growth but evidence was recorded of grazing by rabbits or hares on the young plants and new shoots. The plant population was spread unevenly over the 2ha and there were some patches where no plants existed. In February 2000 the 2ha trial plot showed substantial growth is some areas but was still patchy in others and there was little or no growth in the remaining areas. A definite need to replant certain areas was identified in Spring 2000 and a new plan for replanting was produced by Bical. iv The 2ha plot was replanted by Bical in May 2000. This resulted in some improvement. Weed control was improved although not 100% successful, and the plants appeared healthy, but the field remained somewhat patchy. By the late summer and autumn periods of 2000, a 3.1 increase in the height of plants and a 5:1 increase in the number of emergent shoots were recorded. But growth rates were seen to slow down during the following winter period when plant survival rather than growth is of importance. There was encouraging progress with some substantial growth over the summer of 2001. It will be interesting to see how the plot progresses in the spring of 2002. Since crop establishment has been less successful than anticipated on the 2 ha plot it has not yet been possible to plant the full 12 ha of miscanthus. The trial plot itself will not provide sufficient miscanthus for the combustion trial even by 2003. It has been decided to overcome this shortfall by harvesting miscanthus from a variety of other sites in the area around the Elean Power Station and to bring the combustion trial forward a year. Some harvesting at these other sites was undertaken in October 2001, with baling undertaken within a few weeks of this. To date the yield from these other sites has not been confirmed but has been estimated between 7-9 t/ha. Material is currently being compiled and stored on hard- standings near by the trial plot prior to the commencement of the combustion trial. It is anticipated that harvesting of the trial plot will begin in early Spring 2002 and the final report for this project will describe the harvesting, what happens to the miscanthus subsequently and will include the time taken for harvesting and baling and the costs associated. The intention is to burn the miscanthus at the end of March or early April 2002, at the Elean Power Station.