These include use of conservation tillage techniques, improved soil, pasture, and livestock management, paddy field management, careful use of nitrogenous fertilizers, better tractor operation, and irrigation scheduling as outlined in Table 3.27.
Crop production in heated greenhouses is particularly energy intensive, and in many cases intended to satisfy luxury demands for vegetables grown out of season or cut flowers (Japan Resources Association, 1994). A range of options exist to reduce the energy inputs (CAE, 1996).
|Table 3.27: Uptake of management techniques and new technologies to reduce greenhouse gas emissions in the agricultural sector|
Techniques and technologies to be considered
|Conservation tillage||Conventional tillage consumes 60% of the tractor fuel used in industrialized crop production and decreases soil carbon. Minimum and zero cultivation techniques save tractor fuel, conserve soil moisture, and reduce soil erosion. Uptake is continuing worldwide. Greater chemical weed control may be required. Benefits need to be achieved without reducing crop yields which is more likely under dry conditions as a result of moisture conservation. Animal powered versions of conservation tillage used in developing countries can also reduce the manual drudgery. Cost of uptake in Botswana is around US$31 38/tC saved. Globally 150-175MtC/yr sequestration is possible.||
Allmaras and Dowdy (1995)
UNEP/Southern Centre (1993)
|Soil carbon uptake||Typical agricultural soils contain 100-200tC/ha to 1m depth. Overuse of soils leads to degradation, salinization, erosion, and desertification, and will lead to lower organic matter contents with consequent carbon emissions. A change of land of intensively cultivated soils could result in increased organic matter and carbon sequestration till the soil finds a new balance. Total sequestration potential of world cropland is around 750- 1000MtC/yr for 20-50 years from: erosion control (80-120MtC/yr), restoration (20-30MtC/yr), conservation tillage and crop residue management (150-170MtC/yr), reclamation of saline soils (20-40MtC/yr), improved cropping (180-240MtC/yr) and C offsets through energy crop production (300-400MtC/yr).||
Lal and Bruce (1999)
Takahashi and Sanada (1998)
|Paddy rice||Estimates have been corrected downwards to around 360MtC/yr. Emissions can be reduced by intermittent flooding and greater use of inorganic fertilizers, but these benefits will be offset by increasing areas grown to meet increasing food demand.||
Mosier et al. (1998a)
|Nitrogenous fertilizers||Anthropogenic agricultural nitrous oxide emissions (over 800MtC/yr) released after application of N fertilizers as a result of nitrification and denitrification and from animal wastes, exceed carbon emissions from fossil fuels used in agriculture. Measuring emissions is difficult (±85%) because of soil variability. Reductions resulting from use of N fertilizer strategies, slow release fertilizers, organic manures and nitrification inhibitors, could tentatively cut emissions by 30% on a global scale. Costs would be between US$0 14/tC in Europe for 3-4MtC/yr. Genetically engineered leguminous plants may have further potential.||
Augustin et al. (1998)
Hendriks et al. (1998)
Kramer et al. (1999)
Kroeze and Mosier (1999)
|Correct operation of tractors and size matching to machinery can save fuel, improve tyre life, reduce soil compaction, and save time. Behavioural change by driver education is required but with cheap diesel fuel there is little incentive.||
Sims et al. (1998)
|Irrigation scheduling||Applying water only as needed saves both water and energy for pumping. Cheap and accurate field soil moisture sensors are necessary but not yet available.||
Schmitz and Sourell (1998)
|New technologies||Techniques and technologies to be considered||References|
|Ruminant enteric methane||Average methane emissions of grazing animals in temperate regions are 76.8 kg/head/yr for dairy cattle; beef cattle, 67.5kg; deer, 30.6kg; goats, 16.5kg; and sheep, 15.1kg. Reduction is by either improving the productivity of the animal or reducing emissions by chemical, antibiotic control (vaccines) or biological methods (bacteriocins) without affecting animal performance. Poor animal diet in developing countries produces higher methane per unit of production. A range of options are being researched, but limited economic analysis of mitigation opportunities has been conducted other than in Europe (15MtC/yr at US$0-14/tC). Selective breeding and magnesium licks may be cheap options. The reduction in ruminant livestock numbers caused by reduced demand for meat, milk (for health reasons) and wool products may continue. Since the sources of emissions are dispersed, they will be difficult to measure, and therefore challenging to include within an enforceable trading regime.||
Ullyatt et al. (1999)
|Postharvest crop losses||A reduction in postharvest crop losses could make a significant impact on energy use, particularly in developing countries such as India, where average losses for cereals average 10% up to 25% loss of the harvested perishables including fruit, meat, milk, and fish. Solar drying on the ground leads to vermin and pest losses. Storage in sealed buildings with natural ventilation and solar heated air will reduce losses for minimal energy inputs. For fresh crops, refrigeration and heat pumps are used to maintain the cool chain but energy inputs can be significant. Solar panels on refrigerated truck roofs are technically feasible but not economic.||
|Global positioning systems||Commercially available GPS and GIS systems are available to map then monitor the position of working tractors to enable strategic applications of fertilizers and chemicals to be applied depending on crop yields and soil types. Plantation forest mapping is also used to plan roads and harvests. Energy inputs can be saved as a result.||
|Controlled environment||Crops grown in greenhouses can use less energy per production unit if the available growing area is increased and better control of heating and ventilation occurs. The effects on energy inputs of producing fish by aquacultural methods rather than sea trawling needs investigation.||
There is potential for improving yields of food, fibre, and energy crops yet reducing inputs by using genetic selection or modification. Animals can also be bred to convert feed more efficiently. Transgenetic technologies will be difficult to implement unless publicly supported. Following careful scientific research, including life cycle assessment analyses, and stringent government controls over the release of genetically modified organisms into the environment, then it may be possible that future agricultural production systems will involve lower inputs of nutrients and energy. The extent of the uptake of such developments will be largely based on assessments of risks, benefits, and public perceptions and is hard to predict.
Options to increase soil carbon levels are given in Table 3.27. Emissions of soil carbon of around 0.23tC/ha resulting from cultivation can be reduced by using zero or minimum tillage techniques. However, a reverse of land use activities would soon lose any accumulated soil carbon. In Canada a group of 7 energy companies are paying farmers (through an insurance company acting as an aggregator of credits), CAN$1.5013/ha/yr to change to zero tillage so they can claim the resulting carbon credits for the effective accumulation period (Ag Climate, 1999). The return to farmers depends on the recruiting and support programme costs, scientific proof of higher carbon gains, and the extent to which other on-farm carbon emission reduction activities are implemented.
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