How the farmer's world will change - new problems, new crops, new opportunities

by Bernard Rice of the Teagasc Crops Research Centre

Although the scope for replacing oil with plant-derived fuels is limited, energy crops could readily produce a tenth of Ireland's total energy demand without seriously curtailing other types of agricultural production. But financial incentives will be needed to make this happen.


Although farm-based renewable energy production is the main theme of this paper, three other energy-related issues need to be addressed too. First, the agricultural sector is a major source of greenhouse gas and acid-precursor emissions, and it must expect to come under increasing pressure to reduce these. Second, the cost of the energy input on farms is increasing rapidly, with consequent financial problems for an industry in which profit margins are already tight. Finally, the need to abate national greenhouse emissions may open up opportunities for the use of crops, by-products and wastes for renewable energy production.

This paper will therefore review the position under three headings:

  • The energy input to agriculture, and possibilities for reduction
  • Options for the reduction of greenhouse gas and acid-precursor emissions from present-day agriculture.
  • Possibilities for the development of renewable energy from agricultural crops, by-products and wastes.

The new millennium brought a number of forecasts of the changes that might be expected in Irish agriculture over the next 10 to 15 years. These forecasts reflect the likely impact of factors such as input costs, production technologies, labour cost and availability, market forces, environmental constraints and expected EU agricultural policy. Major changes in the structure of the industry have been forecast, with a much reduced number of much bigger holdings engaged in intensive farming alongside an increased number of small extensive units farmed part-time or in niche activities. However, to date no major changes in the enterprise mix have been predicted (Downey 2000, Donnelly & Crosse 2000). Adjustments to the Common Agricultural Policy may eventually provide the impetus for a move from livestock to non-food production.

The expectation of major structural change, along with the problems caused by BSE and foot-and-mouth disease and the lack of profitability in many enterprises, have led to a fall in morale among farmers. While there is a widespread recognition of the need for new enterprises, the finance and commitment needed to make the transition may be in limited supply. Of Ireland's total land area of 6.9 Mha, at present almost 5 Mha is used for agriculture and forestry. Of this, about 0.5 Mha is rough pasture suitable only for low-intensity grazing. The current use of the remaining land is grassland 3.5 Mha, forestry 0.65 Mha and arable crops 0.4 Mha.


The total energy input to agriculture can be divided into that which is used directly (i.e fuel, electricity) and that which is used indirectly to produce farm inputs (e.g. feedstuffs, fertilisers, plant protection products).

2.1 Direct energy use: Data from the Teagasc Irish Farm Survey indicate that Irish farmers purchased about 258 kt (258,000 tonnes) of oil in 2001 at a total cost of about €140M (Figure 6A1).

Apart from a small amount (possibly 5 kt) used for grain drying, this was used predominantly in the engines of tractors and self-propelled machines. Of an additional €126M spent on road vehicle fuel (mainly petrol), €46M was attributed to farming operations. This is equivalent to about 50 kt of fuel.

The Teagasc survey does not include the fuel that was used by farm contractors. An approximate breakdown of on-farm energy consumption by operation, based on estimates of agricultural production and fuel consumption from various sources as well as Oak P ark experience, is given in Figure 6A1 (O'Kiely et al 2000, Pellizi et al 1995, Postoven & van Daspelaar 1994, Wegener et al 2002). Since most silagemaking as well as some arable crop operations and slurry spreading are carried out by contractors (Figure 6A2), this could bring the total fuel use on farms up to between 370 and 400 kt at a cost of €220-€240M.

In the National Energy Balance (Dept of Public Enterprise website), 278 ktoe (kt of oil equivalent) was attributed to agriculture in 2001. This equates to 269 kt of diesel oil. The Central Statistics Office (CSO) website included in its estimates of inputs to agriculture a total of €298M spent on energy and lubricants. Excluding the expenditure on electricity (€74M) and lubricants (€7M), it is estimated that a total of €217M was spent on fuel oils. Both these estimates are in reasonable agreement with the Teagasc survey results.

Apart from fuel oil, the other significant direct energy use on farms is electricity. This is estimated at 52 ktoe in the National Energy Balance for 2001 and €74M in the CSO input estimates. In the Teagasc survey, farmers indicated that €38M (equivalent to about 30 ktoe) of their expenditure on electricity should be attributed to their farming operations. The discrepancy between these estimates stems from the difficulty in separating farm from domestic use.

The total direct energy input on farms is therefore between 400 and 450 ktoe, or between 18 and 20 PJ. This is about 3% of total final consumption in Ireland, so any reductions that might be achieved in agriculture would have little impact on the total consumption figure. Nevertheless an effort to achieve some reduction in on-farm energy consumption is worthwhile, to improve the profitability of operations that are under severe financial pressure as well as to reduce the contribution from agriculture to greenhouse gas and acid-precursor emissions.

According to the estimates in Figure 6A2, silage-making, tillage operations and slurry handling/spreading are the operations requiring most of the direct energy input. Efforts to reduce the use of energy in field operations can be tackled under the following headings:

  • Using the most efficient tractor-implement set-up: good matching of tractor to machine, appropriate ballasting for high tractive efficiency, use of high-speed pto and high gears for low-power operations, using non-powered implements where possible, increasing working widths to maximum feasible, combining field operations etc
  • Modification of husbandry practices: extending grazing season to reduce fodder conservation, wilting silage, minimising slurry volumes that require storage and land-spreading, elimination of ploughing, adopting non-drying preservation systems for moist grain etc.
  • Good routine maintenance of tractors and other machines.

While research and advice can contribute to some efficiency improvements, it has to be acknowledged that the likelihood of achieving large improvements in the present economic climate is not great. At present, farmers' machinery management decisions are primarily concerned with reducing overhead costs and labour. In some cases this may lead to more efficient fuel use e.g. the hire of a contractor with new, efficient equipment. In other cases it may have a negative effect e.g. extension of machine replacement intervals.

Given that there is likely to be a slight reduction in animal numbers, and some diversion of land out of agriculture into forestry, amenity and building development, as well as some improvement in energy efficiency, a reduction of 15-20% in direct energy input to agriculture would appear to be a reasonable target for the next 5 years. In the longer term, a continued gradual reduction is the most that could be expected.

2.2 Indirect energy use: The major indirect inputs of energy into farming are in the form of animal feeds (mainly imported protein), mineral fertiliser, crop protection products and veterinary products. From an energy viewpoint, fertiliser use is the most interesting. Figure 6A3 shows that nitrogen (N) is the dominant factor linked to energy, and that fertiliser energy input is similar in magnitude to direct energy use (Postoven & van Daspelaar 1994).

In addition to this energy input, N application also contributes to ammonia and N20 emissions from the soil, as well as to the leaching of nitrates to watercourses. So a reduction of N use would have significant benefits for agriculture, provided it could be achieved without loss of crop yield. Possibilities for achieving this will be discussed later.

In relation to current farming, input reduction is the most direct way of reducing emissions. In particular the reduction of N fertiliser would reduce N20 emission as well as energy input. Farmers need to be persuaded not to exceed recommended fertiliser rates. REPS-type programmes and legislative controls will make a contribution in this direction. In the medium term, research will be directed at improving the precision of recommended rates and timings, backed up by the use of decision-support systems. Looking further ahead, techniques for variable-rate application in response to yield maps and soil analysis, will help to make more effective use of reduced amounts of fertiliser.

Taking all the above into account, a reduction of 10% in the total amount of fertiliser used might be considered an achievable target for the next five years, with a further reduction at a similar rate in subsequent years.

Another approach to the reduction of mineral fertiliser input is to achieve a greater substitution of mineral nutrients by animal manure. At present about 400 kt of N is applied in mineral form in Ireland; about half that amount is present in the animal slurry collected on farms (Dept of Agriculture web-site). When farmers are choosing fertiliser application rates, they make little allowance for the N that is present in the slurry, for two reasons. First, an unknown amount of it is lost in conventional splash-plate spreading. Second, the rate at which the slurry N becomes available to the growing crop is less certain than that of mineral N. The first problem could be greatly eased by the use of a low-emission spreading technique, the second could be improved by anaerobic digestion which would make slurry N availability faster and more predictable.

If some progress can be made in the introduction of these technologies, a 10% increase in the substitution of mineral N by slurry N over the next five years should be attainable.


3.1 Greenhouse gases Global warming is set to become a major international issue over the next ten years. Ireland's allocation of a 13% increase in GHG in the period from 1990 to 2008-12 was reached in 1998, and an increase close to 30% is feared unless corrective action is taken. The achievement of the 13% target will require that every possibility for CO2 abatement be fully exploited.

With regard to agriculture, it is reasonable to ask:

  1. 1. How can the emissions from current farming practices be curtailed?
  2. 2. Can agriculture make a contribution to emission reduction, by creating additional carbon sinks or producing biofuels?

The agricultural sector accounts for 35% of greenhouse gas emissions (Figure 6A4, Convery & Roberts 2000, Environmental Resource Management 1998).

This high ratio arises from our big livestock industry, most of whose production is exported. Whatever the reason, efforts to reduce emissions will inevitably focus on the farming sector. Agriculture differs from the other sectors in that it also affects the amount of CO2 that is recycled by growing crops, and the amount that is stored in soil and over-ground biomass.

Of the approximately 24 Mt of CO2 equivalent emissions attributed to agriculture, the major contributors are as in Figure 6A5.

These figures are taken from the ERM report (Environmental Resources Management 1998), with the addition of the CO2 estimated to be associated with direct and indirect energy use on farms.

Methane from in-rumen fermentation can only be tackled by reducing animal numbers or altering their diet. While some reduction in animal numbers may be expected, a large reduction would have serious economic consequences. Diet adjustment would be very difficult to achieve in a largely grass-based industry.

N20 from soils is very difficult to estimate. It would be reasonable to assume that a reduction of N fertiliser would lead to a reduction of N20 emissions, though the extent of the reduction is difficult to predict. This leaves us with the lesser items; N20 and methane from animal wastes, as well as direct energy use and N fertiliser.

3.2 Acid-precursor emissions: In parallel with the Kyoto agreement on greenhouse gases, the Gothenburg Protocol binds Ireland to reductions in acid-precursor emissions over the same 1990-2010 period (United Nations 1999). From the viewpoint of agriculture, ammonia is the main concern, since 90% of ammonia emissions come from agriculture. Agriculture accounts for a much smaller proportion of NOx emissions, but some reduction of the agricultural contribution would still be of value.

The Gothenberg Protocol requires a 9% reduction of national ammonia emissions (United nations, 1999). Of the total of about 120 kt of ammonia emitted from farms, that from pasture would be almost impossible to reduce by any means other than a reduction of animal numbers (Figure 6A6).

Emissions from animal buildings and manure stores would be difficult and expensive to control. The main targets for reduction should be those from the application of mineral fertiliser and from the spreading of animal manure, which account for about 44% of the total.

Of the other acid-precursor emissions, NOx is directly related to combustion. NOx emissions from new and lightly-used tractors in Sweden and Switzerland have been reported at 5 to 15 g/kW h, or 0.42 to 1.27 kg/GJ at 30% engine thermal efficiency (Hannson et al 2001, Rinaldi & Stadler 2002). The US EPA has reported on its web-site average NOx measurements in a tractor fleet of 8.4 g/hp h (equivalent to 11 g/kW h or 0.93 kg/GJ). The Danish RISO National laboratory website lists a NOx emission factor of 1.28 kg/GJ for use with off-road diesel vehicles. This is somewhat higher than the other estimates, possibly because it includes off-road vehicles other than farm tractors which may have longer idling periods. McGettigan & Duffy (2000) have quoted an emission factor for off-road vehicles of 1.15 kg/GJ. If this is applied to an annual fuel consumption of 320- 350 kt, NOX emissions would be about 18 kt. The emissions from the small amount of fuel used in heating/drying would be insignificant. For road vehicles, applying a lower emission factor (0.5 kg/GJ) to the combustion of 50 kt of fuel would give about 1 kt of NOx emissions. This suggests that the total emission of NOx from on-farm fuel use is about 19 kt.

This estimate is considerably higher than the 4.5-5 kt published elsewhere (Curtis 2001, Environment Protection Agency 2001). The difference arises mainly from confusion about the proportion of farm fuel purchases that is used in engines.

Potential for emission reduction:

Anaerobic digestion of slurry would allow the methane to be harnessed for energy use, and thus achieve a double benefit. A recent UK life-cycle analysis has estimated that anaerobic digestion of pig slurry has the potential to reduce emissions by the equivalent of 144 kg of CO2 per tonne of pig-meat produced (Cumby et al 2000). On this basis, 75% adoption by the pig sector in Ireland would reduce emissions by 16 kt CO2 per year. A high adoption rate may be achievable in this sector as the technology would fit in easily on the large centralised units that now make up most of the industry. Also these units are having increasing difficulty finding land nearby for land-spreading, and the smells from slurry transport and spreading are becoming an increasing problem.

The technology would also be applicable to the dairy industry, but is likely to have a much slower uptake. Units are smaller, smells are less of a problem, and to date on most farms the land bank is adequate to take all the slurry. A 10% adoption would abate about 60 kt CO2 per year. The beef sector has had so many recent problems and is generally so unprofitable that it is difficult to envisage investment in anything but the most essential items in the near future.

If digestion could be introduced at the above projected levels over the next five years, a total of about 80 kt/year of CO2 could be abated. An Irish Bio-energy Association report estimates that the total potential for CO2 abatement by digesting all animal manures is 5Mt/year (Irish Bio-energy Association 2000).

A reduction of mineral N usage, or a transfer from urea to ammonium nitrate, would bring about some reduction in the associated ammonia emission. But the main possibility to achieve a substantial emission reduction is to use a low-emission slurry spreading system. Reductions of up to 50% could be achieved with a simple band-spreading technique. If 50% of animal manure were spread with this system, most of the required 9% reduction of ammonia emissions could be achieved.

The main limitation to the adoption of low-emission spreading techniques is the need to improve machine design and all stages of slurry collection and storage and agitation to avoid blockages. The extra cost of spreading would also be a deterrent, and farmers may be expected to continue with the present splash-plate system until they perceive some financial advantage in changing.

In summary, a combination of low-emission slurry spreading systems and slurry digestion could achieve a combination of useful objectives:

  • Digestion would ease the blockage problems that are limiting the uptake of low-emission spreading
  • Both would contribute to a reduction of slur ry smells during spreading.
  • The required 9% reduction in ammonia emissions would be achieved.
  • Methane emissions from animal wastes would be reduced by the equivalent of about 80 kt of CO2.
  • Crop utilisation of slurry N would be quick er and more predictable, so the opportunity to substitute slurry N for mineral N would be increased.

On this basis, a substitution of 10% of the applied mineral N by slurry N might be achievable over a five-year period.

A quick reduction of NOx emissions from agriculture would be difficult to achieve. The fall in fuel use projected in Section 2.1 would bring a corresponding reduction in NOx emissions. In the long-term, a 3-tier schedule of regulatory emission controls aims to halve NOx emissions on new off-road engines by 2010. In the interim, the methods that might be considered to achieve a more immediate reduction of NOx emissions would be:

  • Retro-fit catalytic converters, while tightening fuel specifications to prolong converter life
  • Persuade users to reduce idle and low-load running of tractor engines, when NOx emissions are highest.

Many difficulties could be foreseen in the implementation of either action.


4.1 Overall potential: The total potential for energy production from agriculture can be estimated by adding the potential from energy crops to that from by-products of existing enterprises. From crops converted by some form of combustion to heat, an energy yield from 100 to 200 GJ/ha might be achieved, depending on the crop selection, land quality etc. Assuming that an average energy yield of 125 GJ/ha could be achieved, the current set-aside area could produce about 4 PJ, or 11% of the total agricultural energy demand. To achieve, say, 10% of national primary energy requirement from biomass crops, an area of over 0.5Mha would be required, i.e. more than the current arable area (Fig. 6A7). At the extreme, the total Irish land resource could just about produce our national primary energy requirement.

Potential for energy production from crops grown for direct combustion (forestry, coppice, hemp, miscanthus, whole-crop cereals etc) and for liquid biofuel production (rape-seed, cereals, sugar-beet etc). TPER stands for Ireland's Total Primary Energy Requirement.

Crops grown for liquid biofuel production (e.g. rape-seed for biodiesel, cereals or beet for ethanol) would produce a lower amount of energy, probably about 60 GJ/ha. Crops for these purposes are more likely to be annual arable crops. If the full arable set-aside area were devoted to them, it would produce about 1.8 PJ, or 40 ktoe, i.e. about 15% of the agricultural fuel requirement. To supply the full agricultural fuel oil need would require almost all the current arable area to be devoted to it.

The main by-product materials that could make a contribution are as in Figure 6A8.

Some of these materials (e.g. molasses, some straw) have existing markets which underpin their price; others have more limited outlets. Also materials such as slurry from small dry-stock units could hardly be utilised economically, and forest residues would be better left in situ on many sites. A rough estimate of the volumes that might be available at a reasonable price and the amount of energy they might produce is also given in Figure 6A8.

4.2 Biofuel technologies: Of the many possibilities for producing biofuels from farm produce, three of the more likely possibilities for Ireland are considered here:

  • biogas from animal slurry
  • heating or diesel engine fuel from vegetable oils or animal fats
  • ethanol from sugar beet, cereals or cellulosic materials.

4.2.1 Biogas from animal slurry: This has already been discussed in detail. If the targets mentioned for slurry digestion were achieved (i.e 10% of dairy slurry and 75% of pig slurry digested), about 10 MWe of electricity could be generated from the biogas produced. This is a much more conservative estimate than that of the Irish Bio-energy Association (IrBEA), who suggest that 250 MWe could be produced from biogas (IrBEA, 2000).

4.2.2 Oils and fats as heating or diesel engine fuels: Vegetable oils and animal fats can provide a source of renewable fuel, either for diesel engines or heating systems. Some of these uses are already well developed, others are still under development (Fig. 6A9).

Any of these uses would reduce CO2 emissions by over 3 tonnes per tonne of fuel used. Also these fuels have no sulphur, which improves exhaust emissions, and they are biodegradable, which reduces pollution risks from spillages. These materials could never replace more than a small fraction of the mineral diesel requirement. They should be seen instead as premium fuels whose use should be directed to applications that make best use of their health and environmental advantages.

Oils and fats can be used as engine fuels in two ways:

1. In unprocessed form, with some peripheral modifications to the engine. This use is relatively new but developing rapidly in Germany; engine conversion kits are on sale and are working very well. The conversion consists of some combination of fuel pre-heating, extra filtration, increased injection pressure and replacement injectors. More information on exhaust emissions is needed. Fuel processing cost and industry start-up costs are kept to a minimum. This approach would have particular relevance in Ireland; it needs a low capital investment, the by-product cake can be used locally, and it is possible to start small and expand later.

2. Converted into biodiesel and used in any engine without modification. This use is widely accepted and supported by the vehicle industry. Also the fuel has been proven to emit less particulates and smoke than mineral diesel. This reduces the harmful effects of exhaust emissions in cities. About 1Mt/yr is produced and used in the EU. It requires substantial plant investment, and processing adds about 5-10 cents/litre to the final cost of the fuel.

The use of these fuels for heating in large-scale burners is technically feasible, but economic viability depends on a very low raw material price, competitive with heavy-grade mineral oil. Use in domestic-scale heating units would be more economical, but the availability of suitable burners at a reasonable price remains a problem.

Currently, the main fuel use of oils/fats in the EU is biodiesel produced from crops grown on set-aside land: mainly rape in N. Europe, with some sunflower in the south. Oil-seed crops grown on set-aside in Ireland would also provide as a by-product a native source of GM-free animal feed protein, which would find a ready market. Ireland has about 30,000ha of set-aside; if two-thirds of this could be brought into oilseed production, it would provide about 20 kt of fuel oil and 40 kt of oil-seed cake.

A cheaper raw material is recycled vegetable oil (RVO) oil from caterers. The use of this material in animal feeds has been disrupted since the 1999 Belgian dioxin-in-chickens incident, which was traced to RVO. If no alternative use is found in the Republic, two possibilities arise:

  • Collection will shrink, and more will be dumped into sewers and land-fills.
  • It will be exported for biodiesel production to Northern Ireland, which will benefit from the introduction of a 20p/litre excise remission announced in their 2002 budget.

Up to 10 kt/year could be collected. Oak Park research, together with research and practical experience in Austria, is showing that it can be used to make good quality biodiesel.

Beef tallow, whose market as an animal feed has been disrupted by BSE, is another possibility. The disposal of tallow from the rendering of BSE-risk offals (ca. 3000t) has been resolved by its use in boilers in rendering plants. Total tallow production is about 60 kt, two-thirds of which goes to animal feed. The long-term future of tallow as animal feed is in some doubt, and alternative outlets are very desirable. Its use for heating is already being demonstrated, but a transport use would have a higher value.

Biofuel technologies are still relatively new. While the price difference between them and fossil fuels has narrowed significantly in recent years, they still need some pump-priming support in the early stages of competition with fossil fuels. Present costs vary from about 30 cents/litre for clean RVO used unprocessed to 55-65 cents/litre for biodiesel from fresh rapeseed oil. This compares with about 30-40 cents/litre for mineral diesel before excise, VAT and distribution costs.

Subsidy for biofuels could be justified on many grounds:

  • Reduction of greenhouse gas emissions
  • Reduction of harmful exhaust emissions from diesel engines
  • Recycling of organic materials currently in or heading for the waste stream
  • Provision of native, renewable fuel supply with associated economic activity
  • Development of renewable fuel technologies that will be needed in the future
  • Compliance with substitution obligations in upcoming EU Directive proposals

Some EU member states (e.g France, Germany, Italy, Austria and Spain) promote vehicle biofuel production by reducing road excise. This support mechanism is permitted by the EU. The Scandinavian countries promote all forms of biofuel use by means of their carbon tax regimes. In the UK, a remission of 20p/litre on biodiesel was introduced in 2002. At this stage, virtually all of Europe except Ireland has some form of support for vehicle biofuels. The UK measure is likely to stimulate considerable biodiesel production, and in the absence of similar action here, a cross-border traffic in feedstocks is likely to develop.

The EU is now considering proposals from the Transport Directorate to oblige member states to achieve target substitution rates of mineral fuels by their equivalent biofuels. The targets proposed begin with 2% by December 2005, extending to 5.75% by 2010. To meet the 2% target on the diesel side, Ireland would need to use 70kt of oils/fats as vehicle fuel. This would be very difficult to achieve. A possible combination of feedstocks would be as follows:

  • 20 kt rapeseed oil from 20,000ha set-aside
  • 40 kt tallow
  • 8 kt Recycled Vegetable Oil (RVO)

This would supply most of the buses and taxis in Dublin. If the fuel were used in this way it would achieve the following:

  • Halve the amount of particulates emitted by these vehicles
  • Reduce CO2 emissions by about 200 kt:
    Reduce sulphur emissions, and consequent acid rain damage to buildings
  • Maintain the viability of rendering plants.
  • Sustain jobs in RVO collection services and farms.
  • Achieve the mineral diesel substitution target contained in the EU's proposed directive

At a similar level of support to the proposed UK excise remission, the maximum cost to the exchequer would be 15M euro/yr. The combination of all the benefits from the project would well out-weigh this cost. Unlike the UK proposal, the support should be provided for any use of vegetable oils or animal fats as vehicle fuels. The market could then dictate which technologies are most appropriate in Ireland.

4.2.3 Ethanol as vehicle fuel There are two likely ways in which ethanol could be used as fuel for spark-ignition engines in Ireland:

(i) Petrol-ethanol blends may be used in conventional unmodified spark-ignition engines. An EU directive permits the use of up to 5% ethanol in blends with petrol (Commission of European Communities, 1985). This approach is widely used in the US, but has not been favoured in the EU, due to technical problems with the handling and storage of the fuel, caused by its solubility in water and high vapour pressure.

(ii) Blends of the ethanol derivative ETBE (ethyl tertiary butyl ether) and petrol may also be used in unmodified engines. The 1985 directive authorises up to 15% ETBE in blends. This has been the most favoured approach to ethanol use in the EU. ETBE can replace MTBE as an octane enhancer in lead-free petrol. MTBE is in the process of being banned from this use in California, due to the contamination of water supplies by exhaust emissions. If this trend becomes widespread, it would stimulate the demand for ETBE. A problem in Ireland would be the additional plant requirement for the conversion of ethanol to ETBE.

A Teagasc review has dealt with this subject in detail (Rice et al 1997). Total production costs have been estimated for conventional and lignocellulosic materials in tables 6A10 and 6A11 which show a range of production costs from 47 to 73 cents/litre, depending on the feed-stock materials, feed-stock price and transformation process.

Ethanol has a calorific value about two-thirds that of petrol. On this basis, its value as a petrol replacement, before tax or distribution cost, is less than 25 cents/litre. A comparison with the price of methanol, based on its octane-enhancing properties, would give it a similar value. Even a full remission of road excise would make only the lowest-cost wood-chip scenario competitive; further economies would have to be achieved to reduce costs with all the conventional conversion systems.

The main advantage of ethanol production as an outlet for arable crops is that it can be produced from such a wide range of feed-stocks, many of which are already being grown, so the technology for production, harvesting, drying and storage is already in place. If used as an additive to petrol, a distribution and marketing system is also in place, so the process plant is the only additional requirement.

In spite of the apparently unfavourable economics of bio-ethanol production to date, it has become well established in the US, where production is stimulated by the need to oxygenate mineral fuels to comply with clean air legislation. Current US long-term projections are for an industry producing large volumes of bioethanol from low-cost by-product or residue ligno-cellulose materials at a cost approaching that of petrol. The long-term availability of suitable raw materials in Ireland, and the benefit of a low-value outlet for by-product or residue ligno-cellulose materials, needs to be further evaluated.

Ethanol production from sugar beet merits special consideration because of its potential synergistic relationship with the existing sugar industry. Facilities are already in place for the organisation of crop production under contract, and for transport, reception, pre-cleaning and juice extraction; only the fermentation and distillation plant would need to be added.

Ireland currently plants about 35,000 ha of sugar beet. Land for the production of extra beet would be available; with sugar yields continuing to increase and at best a constant sugar quota, it would at least ensure that the area under beet would be maintained at current levels for the medium-term future. Sugar beet is a high-input crop; as well as creating a demand for farm labour and other inputs for the production of the crop, it also generates many spin-off benefits, such as animal feed supply, labour for haulage and processing, and local farm machinery production.

Beet for ethanol production would not be grown on set-aside land, so it would not compete for land with a vegetable oil industry. Teagasc estimates the variable costs of sugarbeet production for 2002 at 1462 Euro/ha (O'Mahoney, 2001). At the B-quota price of about 35 Euro/t, a yield of 42 t/ha would be required to recoup these costs. Given that this is close to the average yield, beet production at this price might be expected to have limited attraction for growers. However, other issues, such as the avoidance of outside-quota prices in high-yield years, would also play a part in farmers' decision-making.

A bio-ethanol industry would make only a small contribution to the reduction of CO2 emissions, as a result of the relatively large amount of energy used in processing.

The main advantages of bio-ethanol as an additive to petrol are:

(i) its oxygenating effect, leading to a reduction of CO in vehicle emissions and a reduced potential for ozone formation in the atmosphere.

(ii) its effect as an octane enhancer, as an alternative to lead compounds or MTBE.

(iii) the absence of sulphur.

(iv) reduction of hydrocarbons in the emissions.


Given that there is likely to be a slight reduction in animal numbers, and some diversion of land out of agriculture into forestry, amenity and building development, as well as some improvement in energy efficiency, a reduction of 15-20% in direct energy input to agriculture would appear to be a reasonable target for the next five years. In the longer term, a continued gradual reduction is the most that could be expected. A reduction of 10% in the N fertiliser input, with a corresponding reduction of indirect energy input, might also be considered an achievable target.

Since much of the greenhouse gas emissions from agriculture are very difficult to control, the scope for reduction is limited. Nevertheless, some reduction is attainable. Figure 6A12 indicates how a reduction of over 9% could be achieved over the next five years.

The reduction in methane from animals is projected on the basis of a small reduction in animal numbers. The reduction in N20 from soils and in fertiliser energy would be achieved by a reduction in mineral fertiliser use, which in turn would be partly due to a fall in overall N application and partly due to an increased substitution of slurry N. The fall in direct energy input would be mainly achieved by greater efficiencies in machinery use. Finally, the production of methane and the use of oils and fats as fuels could contribute an abatement of up to 300 kt. The reduction of N use in urea form and the adoption of low-emission manure spreading techniques could make up the required 9% reduction in ammonia emissions. There would be a synergistic effect from the simultaneous introduction of digestion and low-emission spreading; digestion would reduce blockages, and full-width spreading should give more even distribution and facilitate substitution of mineral N.

The other benefits that would accrue from the developments listed above would be:

  • A reduction in slurry spreading smells
  • An improvement in vehicle exhaust emissions from biofuel use
  • A secured outlet for recycled vegetable oil (RVO) and tallow
  • A start made to the development of technologies which will undoubtedly be required in the future
  • A contribution made to compliance with EU requirements in relation to greenhouse gases and acid precursor emissions, air quality and liquid biofuel substitution.

In all these areas, technologies are now well established and in practical use in other EU countries. Such incentives as have been available in Ireland to date to stimulate renewable energy production have not been sufficient to stimulate the establishment of viable projects. To allow a beginning to be made, two changes are needed immediately: a reduction or remission of road excise on biofuels and an increased price for electricity from biomass. Since the size of the biomass resource is limited and no exchequer costs are incurred until the renewable energy is produced, these measures could be introduced with very little risk to the economy.


This paper addressed three inter-linked problems related to energy in agriculture:

  • The energy used in farming and ways of reducing it
  • The options for the reduction of greenhouse gas and acid-precursor emissions
  • The possibilities for renewable energy production.
Engine fuel (almost 0.3 Mt) is agriculture's main direct energy input. Since there is likely to be a slight reduction in animal numbers and some diversion of land out of agriculture, as well as some improvement in energy efficiency, a reduction of 15-20% in this input over the next five years would appear to be a reasonable target. In the longer term, a continued gradual reduction is the most that can be expected.

Nitrogenous fertiliser (N) is the biggest indirect energy input. With greater precision in N use, and an increased substitution of slurry for mineral N, a reduction of 20% over five years without reducing output should be achievable.

With agriculture contributing over one-third of national greenhouse gas emissions, pressures for reduction must be expected as the effort to achieve Kyoto targets intensifies. Some abatement of ammonia emissions is also required to comply with other international commitments. To achieve both of these targets without reducing output, digestion and low-emission spreading of animal slurry to minimise methane and ammonia emissions are the most promising options.

If liquid biofuel crops (for vegetable oil or ethanol) were grown on the existing set-aside area, it could supply about 10% of the agricultural fuel demand. To meet the full agricultural fuel demand, an area of about 0.3Mha (6% of the farmed area) would be needed.

Where the whole of an energy crop is utilised in a heating or CHP plant, about 0.5Mha would be required to meet 10% of the total national primary energy demand. This could be set as a medium-term target that could be achieved without major disruption of the existing levels of food and feed production. At the extreme, the total farmed area could produce an amount of energy roughly equivalent to our national primary energy demand.

Waste or by-product materials such as wood residues, straw, tallow and recovered vegetable oil would produce relatively small amounts of energy, but as reasonably-priced feedstocks they could help get biofuel industries started. Animal manures have a large potential, and their digestion could play a key role in the reduction of methane and ammonia emissions. Digestion of all pig and some dairy slurry should be a medium-term target.

The most promising technologies for the conversion of farm biomass to energy are:

  • Vegetable oils and animal fats as engine fuels in vehicles or CHP plants: this would entail the conversion of either the fuel to biodiesel or the engine.
  • Ethanol as a replacement for MTBE in petrol, either converted to ETBE or used directly: this might be produced from sugar-beet and sugar processing by-products, from cereals, or eventually from wood-waste.
  • Methane production from animal slurries, used in heating or CHP plants.
  • Direct combustion or gasification of wood or other energy crops in heating or CHP plants or as domestic fuel.

In all these areas, technologies are now well established and in practical use in other EU countries.


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This is one of almost 50 chapters and articles in the 336-page large format book, Before the Wells Run Dry. Copies of the book are available for £9.95 from Green Books.

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