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resent European agricultural policy framework stimulates research on renewable energy like energy crops. “Energy self-reliance in organic farming – is it feasible?” was the subject of the work-shop of the international society of organic Pfarming research (ISOFAR) organised after the Organic Congress in Denmark in the early summer of 2006. Contri- butions to the workshop mainly dealt with production of energy crops and derived fuel and biogas. Energy self-suffi ciency and a closed nutrient cycle is a basic principle of organic farming ever since. However, does this mean that the mission of organic farming includes both food production and energy production for consumers outside the farm organism? This question rose but was not discussed offi cially hence the majority of the attendants shared the opinion, that the main concern of organic farming is production of food. Here I compare effi ciencies of energy crops with technical alternatives of renewable energy production. As an example, I present production of rape as energy crop.

Energy crops and renewable energy: overall and process effi ciency

Engineering: the Cinderella of intensity is about 1000 kWh/m2 and year. organic farming research? The effi ciency of photosynthesis confi - Engineering sciences lead a shadowy nes the energy yield and reaches in the existence within organic farming re- tropics about 5 % of solar radiation. The search. However, agricultural machinery maximum technically possible energy and buildings cause up to 40 % of the yield in Finland may reach up to 22,2 production cost in organic farming too. kWh/m2 or about 40-fold the average The high costs of technical input force of energy input of Finnish agriculture. towards specialisation of farm produc- On principle, the caloric yield of crops tion, narrow crop rotations and depen- decreases with raising energy density dency from fossil fuels and counteracts of the crop component: Lignin > starch to organic farming principles. However, > sugar > oil. This means, that oil crops a physical and technological approach produce less energy per ha and year than and engineering profi ciency may con- sugar beets, potatoes, reed canary grass tribute to the aims of organic farming or wood. in respect of energy issues too. The crop scientist focuses his research on high Process energy of cultivation quantity and quality of yield based on a The energy input for crop cultivation sustainable tilth. The engineer interprets that is the energy yield divided by the varies in a wide range depending on ha- this approach as maximisation of photo- overall energy input. The energy yield bitat, crop species and variety, intensity synthesis effi ciency. As an example of is the calorifi c value of the biomass or of production, and employed tools and the involvement of engineering sciences the derived fuel respectively. The most machinery. Generally Finnish agriculture methods, I use rape as energy crop. I important energy source of crop produc- consumes in average 0,75 kWh/m2 and compare the results from a literature re- tion is the solar radiation followed by year of which 0,3 kWh/m2 and year are view with effi ciencies of solar techniques the energy input caused by cultivation fossil fuels. The engineer considers the using solar energy without diversion into measures like tillage and harvest and cultivation measures as a production photosynthesis. the energy demand for processing the process and calculates the process ef- biomass into fuel. Both, the annual solar fi ciency dividing the energy yield by The sun is the source radiation intensity and the crop cultiva- the energy input from seed to harvest. of renewable and fossil energy tion area are limited locally and world- Numerous research results show that The sustainability of energy crop pro- wide like the fossil energy sources too. the process energy of organic farming is duction depends on the overall effi ciency In southern Finland, the solar radiation substantially better than that of conven-

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tional farming systems. However, this benefi t is negligible if we calculate the Meal overall effi ciency including the energy input from solar radiation. The fi rst two Oil columns of fi gure 1 show the energy Heat burning input for rape production. seed and straw Root, straw Process energy to convert and seed biomass into fuel Esterifi cation The most effi cient way to use biomass Output Extraction and as renewable energy is to burn it for refi niing Input heat production. The effi ciency depends Production of only on energy input for transport of rape biomass and ash and the effi ciency of Solar radiation intensity the heating system. Additional treatment 0,01 0,1 1,0 10,0 100,0 1000,0 like pelleting, extraction of oil, anaerobic Input/Output kWh/m2 and year digestion, ethanol fermentation etc. may considerably raise the process energy Figure 1. Energy input for production and processing of rape and energy output of rape and input. According to leading American rape processing products. Please, note the logarithmic scale. scientists, the production of ethanol from maize causes always a negative energy Production of balance due to the thermodynamic laws. RME Breeding energy crops and improved process techniques may lead to better Production of oil energy effi ciencies. Crop processing may result in several different products. Some Production of of these products may be used for energy rapeseed production others for fi bre production, Heat burning human nutrition or animal feed. This fact seed and straw causes a methodical problem, called allo- 0% 200% 400% 600% 800% 1000% cation. E.g., the rape crop produces both straw and seeds. However, how to split Figure 2. Energy effi ciency of production of straw and seed, rapeseed, oil, and rape methyl the energy demand of the production ester (RME). 100% means, that energy input is equal to energy output. process between straw and seed? More- over, how to split the process energy de- culate the process effi ciency by dividing fodder, the effi ciency of RME still rises mand between rape methyl ester (RME), the energy output of the fi nal product according to the allocation ratio. rape meal, and glycerine after extraction, (straw and seed, rapeseed, oil, and rape refi ning, and esterifi cation of rapeseed methyl ester (RME) respectively) by the Overall effi ciency oil? Depending on the allocation method, sum of the energy input presented in If we include the solar radiation as en- the energy balance results vary in a wide fi gure 1, except solar radiation energy ergy input into the effi ciency calculation, range. Figure 1 shows additionally the input. This fi gure shows very clear, why the overall effi ciency falls dramatically, energy input for processing of rapeseed rape seems to be a suitable energy crop see fi gure 3. Even doubling the rapeseed into fuel and the energy yield or energy for organic farming too: The energy yield improves the overall effi ciency content of the whole plant and proces- output of straw and seed exceeds 6.5 to only marginally. In turn, the improved sing products as energy output. 9.5 fold the energy input for production. process effi ciency of organic rape pro- Even after processing the rapeseed to duction raises the overall effi ciency only Production effi ciencies RME, we have an energy surplus up to a little bit. The whole rape crop (root, Figure 2 shows the production effi ciency 40 %. If we allocate the energy input to straw, and rapeseed) contains only 3 to of rape and its processing products. I cal- RME and meal, which can be used for 6 ‰ of the overall energy input, RME 1

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Thermal collector

Photovoltaic collector

Production of RME

Production of oil

Production of rapeseed

Heat burning seed and straw

0,01% 0,1% 1,0% 10,0% 100,0% Overall effi ciency

Figure 3. Overall energy effi ciency of production of rapeseed and straw, rapeseed, oil, and rape methyl ester (RME) compared to solar energy harnessing technologies. Please, note House using solar energy. the logarithmic scale. Photo: W. Schäfer. to 2 ‰ yet. We may continue the chain of technical processes to convert bio- to produce hydrogen as well as liquid and feed the meal as protein fodder for mass into fuel justify the production of carbon hydrates from carbon dioxide and dairy cows. Then we win about 34 % of renewable energy from organic waste, water powered by solar energy without the fodder energy as manure. Anaerobic particularly on-farm. The present objec- diversion into photosynthesis. ■ digestion of the manure and the glyce- tives of the EU-energy policy, to develop rine, a by-product of esterifi cation, may energy crop production is captivating Winfried Schäfer add 0.2 to 0.5 ‰ of the input energy. For with various win-win situations: envi- E-mail: winfried.schafer@mtt.fi comparison: The effi ciency of the pho- ronmentally neutral bio-fuels replace tovoltaic solar collector is 40 to 140 fold polluting fossil fuels, farmers get better Dr. Winfried Schäfer is an Agricultural compared to electric power production prices for energy crops, the agrochemical Engineer and works as Principal Research from incineration of the whole rape plant industry gains from intensifi cation of en- Scientist at MTT Agrifood Research Finland, or incineration of methane produced by ergy crop production, turn over of power Animal Production Research, Milk and Beef anaerobic digestion of the whole rape industry grows due to increasing energy Production. He is special-ised in agricultural plant. The effi ciency of the thermal solar consumption to produce agrochemicals engineering in organic farming. collector exceeds the heat production and to process biomass into fuel. As a from incineration straw and rapeseed following, the state tax income improves 100 to 400 fold. However, storage and too. Because in the future the major part continuously production of solar heat of biomass comes from tropical countries Literature: or photovoltaic electric power is very due to the higher overall efficiency, Centi , G., Perathoner, S. (2006): Converting limited. Consequently, future biotechno- environmental pollution is exported CO2 to fuel: A dream or a challenge? logy will focus on producing hydrogen to developing countries at the expense The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006 as well as liquid carbon hydrates from of food production. Organic agricul- http://oasys2.confex.com/acs/232nm/ carbon dioxide and water powered by ture should not resume energy crop techprogram/P990579.HTM solar energy. production but produce high quality Patzek, T. (2004): Thermodynamics of the food environmentally friendly. Organic Corn-Ethanol Biofuel Cycle. Critical Reviews in Plant Sciences 23:519-567. Conclusions agriculture is capable to cover its own Schäfer, W., Luomi, V., Palva, T., Parmala, The technical effi ciency of the photosyn- energy demand from organic waste. S., Ahokas, J. (1986): Kasviöljyt diesel- thesis is too low to replace sustainable Sustainable replacement of fossil fuels moottorin polt-toaineena. VAKOLAn fossil energy sources by energy crops. outside agriculture is reasonable only by tutkimusselostus 42: 37 p. However, the high process effi ciencies employment of bio-technical processes

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