Energy for Agriculture
Introduction
Modern agriculture needs modern energy - the two are closely linked. For many developing countries, agriculture is the dominant sector in developing the economy. Increasing productivity and the modernisation of agricultural production systems are the primary drivers of global poverty reduction and energy plays a key role in achieving this. Energy input to modern and sustainable agricultural production and processing systems is a key factor in moving beyond subsistence farming towards food security, added value in rural areas and expansion into new agricultural markets.
In many cases, renewable energy technologies and hybrid systems can provide energy services that neatly support the production process, e.g. by providing irrigation (pumps) or post harvest treatment (cooling) or processing (drying, milling, pressing). The requirements of mechanical energy in the agricultural production process are also of critical importance and include human and animal labour as well as fuels for mechanisation, pumping and other activities, and indirectly the production of fertilisers and agrochemicals.
The agricultural production chain involves the following steps:
- Production
- Postharvest and storage
- Processing
- Commercialisation.
Production
Land preparation, cultivation, harvesting and threshing
The power necessary for agricultural production is provided by human labour, draught animals or engine-driven machinery. Mechanisation is a key input in any farming system applying tools, implements and machinery to improve the productivity of farm labour and land. Based on the power source, the technological levels of mechanisation have been broadly classified as hand-tool technology, draught animal technology and mechanical power technology.31
The bulk of direct energy inputs in smallholder production is provided by human and draught animal power (DAP). Agriculture in developing countries relies heavily on the physical capability of farmers, with often limited output, depending on the physical energy available. A fit person consumes around 250-300 W in terms of energy, depending on climate and with a rest of 10-30 minutes/hour. The efficiency of energy conversion is only 25 per cent, with a maximum power output of 75 W. Operations involving human skill include activities such as planting, weeding, spraying and harvesting and using hand tools. Most horticultural commodities are harvested manually, including those grown in highly industrialised nations. Energy requirements during harvesting include mechanical energy for digging up root and tuber crops. For example, a simple, labour-saving cassava harvesting tool was introduced to Thai farmers by the International Centre for Tropical Agriculture (CIAT) reducing person-days from 15-40 (depending on the type of soil and the yield) to 5-10 days only. The tool costs 2.50 USD, is produced by local manufacturers and can be used collectively by farmers.32 Harvesting early in the morning when air temperatures are cooler also helps to reduce energy requirements and cooling costs.
Activities such as ploughing, soil preparation, water lifting, pulling inputs and threshing require fewer skills but greater energy input and are hence mostly powered by draught animals such as buffalos, horses, donkeys, camels or oxen. Power output ranges from 200 W for a donkey for 4 hours daily work to over 500 W for a buffalo (FAO 2000a). Draught animal power can alleviate human drudgery and is generally considered to be an affordable and sustainable source of power for smallholders, also given its great potential for diversification and expansion e.g. for transport and non-farm work. Efforts to expand the use of draught animal power should include work on animal efficiency, which can be improved through modernisation of equipment, better breeding and animal husbandry, feeding and veterinary care.
In sub-Saharan Africa (SSA), human effort contributes about 65 per cent of the power required for land preparation and subsequent weeding, the principal demand peaks in the farming cycle. An example comparison shows that a typical farm family relying solely on human power can cultivate only 1.5 hectares per year. This rises to 4 hectares if animal power is available and to over 8 hectares if tractor power can be accessed (FAO 2006).
Transition to increased mechanisation of agricultural operations occurs using diesel or gasoline-powered tractors and harvesters. Fuel powered two-wheel tractors are often used for agricultural production, with different attachements for tillage, bed planting, row planting, harvesting and threshing. In Bangladesh, power tillers (12-15 hp) are used for about 70 per cent of farm work because of their versatility (UNDP/PA 2009). The fuel requirements for digging up root and tuber crops, e.g. of a potato digger are 0.57 gallons of diesel fuel per ton of product (1.96 litres/MT) (USAID 2009). Energy use depends mostly on the speed at which activities are carried out. As tillage operations within arable farming systems often have the highest energy requirements and lead to soil degradation, the reduction of mechanical tillage is promoted by the approach of conservation agriculture (CA).
In general, a four-wheel tractor will not be economically feasible for a smallholder with a typical land holding of up to 5 hectares. Government-run tractor hire schemes in SSA countries have not been able to increase farm productivity. On the other hand, the concept of a rental market for privately owned and operated tractors has potential that may increase in the future (FAO 2006).
In general, a four-wheel tractor will not be economically feasible for a smallholder with a typical land holding of up to 5 hectares. Government-run tractor hire schemes in SSA countries have not been able to increase farm productivity. On the other hand, the concept of a rental market for privately owned and operated tractors has potential that may increase in the future (FAO 2006).
Besides direct energy demand in agriculture there are also indirect energy inputs in the form of sequestered energy in fertilisers, herbicides, pesticides, and insecticides, all of which require energy in their production, distribution and transport processes. Fertilisers form the largest of these energy inputs to agriculture, whilst pesticides are the most energy-intensive agricultural input (on a per kg basis of chemical) (FAO, 2000).
Need for these inputs however can be reduced by the use of farm-own organic manure or by agro-industry based bio-fertiliser production, e.g. generated from biogas plants (at household or industrial level). The promotion of locally produced organic fertiliser also has the advantage of avoiding the negative environmental impact of mineral fertilisers and benefits from the shorter distances required for distribution, thus reducing energy requirements and fuel costs.
Past experience in Asia indicates that the key factors driving mechanisation and consequently power for agricultural development are guaranteed markets and farm prices for key crops, favorable government policies and availability of credit. The example of India shows that favorable government policy and farmer demand have led to increased availability of appropriate and locally manufactured farm machinery and ultimately to India becoming the world‘s largest tractor manufacturer.
A very comprehensive comparison of Energy Use in Conventional and Organic Cropping Systems has been carried out by the National Sustainable Agriculture Information Service (ATTRA) of the US National Centre for Appropriate Technology (NCAT). The report shows, in a review of existing studies, that there are many complexities involved in comparing energy consumption in conventional and organic cropping systems. Certain research indicates that organic agriculture is more energy-efficient than conventional agriculture, but not in all cases. In some cases, organic agriculture may be more energy-intensive, depending on the specific farming operation, the crop produced and the post-production handling. It is important to assess the energy-intensiveness of food systems in a holistic manner that incorporates energy consumption for the entire life cycle of the food product.
Irrigation
Access to water is a major determinant of land productivity and active water management through irrigation offers an important opportunity to stabilise yields. Irrigation is therefore of the utmost significance in the agricultural production process and this chapter is consequently accorded great importance. Irrigated land productivity is more than double that of rainfed land. In sub-Saharan Africa, only 4 per cent of the area in production is under irrigation, compared with 39 per cent in South Asia and 29 per cent in East Asia (World Bank 2007). With growing water scarcity and costs of large-scale irrigation schemes rising, there is a need to enhance productivity by improving existing schemes, expanding small-scale schemes and developing water harvesting.
―Irrigation‖ refers to the distribution of water for growing crops, including the use of water storage and pumping, where appropriate. The energy demand for irrigation purposes is the energy required to lift water by pumping from surface sources, such as ponds, streams, or canals; or from below-ground sources using open wells or boreholes. This water is typically pumped to surface canals, reservoirs, or elevated tanks. The energy demand for water lifting is calculated by multiplying the head (the vertical distance from the water source to the field in metres) by the volume of water to be raised in cubic metres (m3). Pumping energy needs are typically expressed in units of m4.
Decisions about energy and irrigation should be made on the basis of three key sequential steps:
- Choosing the right irrigation technology: understanding the irrigation system needs for a given context,
- Choosing the right pump technology: understanding the various pumping technologies available,
- Choosing the right energy source: assessing which power sources are possible, desirable, and locally available to provide the necessary energy for that system.
Choosing the right irrigation technology
The question of which irrigation water distribution system is most suitable will depend on several factors including the crop(s) cultivated, climate, location, scale/area of agricultural production, quantity of water required over time, system cost, access to capital, local agricultural workers‘ technical capacity, local availability of equipment, maintenance and repair services and availability of spare parts. Irrigation systems differ in their peak and average water requirements, the need for water storage (e.g. tanks, cisterns), and the ultimate need for pumping and energy. Where small producers (<two hectares) are targeted, the more expensive irrigation technologies may only be accessible through membership of cooperatives and farmers‘ associations, who have sufficient ability to raise capital, as well as having the management capacity for technology adoption, operation, maintenance, and replacement. The reliability of the selected irrigation system and the ability of its maintenance is of primary importance for farmers.
Post-harvest and storage
Processing
Commercialisation
Further Reading
- GIZ-HERA (2011): Modern Energy Services for Modern Agriculture - A Review of Smallholder Farming in Developing Countries.
