Land availability.
Environment.
Economics.
Constraints.
There are three major factors to consider if biomass is to play a significant role in future (to 2050 at least) energy, supply scenarios.
Firstly, the supply of the biomass energy feedstock has the ability to improve the efficiency with which agricultural and forestry land is used in developing countries. In industrialised countries, the supply of biomass energy feedstock could provide non-food feedstocks from marginal and excess agricultural land, large areas of which are planned to be set-aside in the near future. Biomass has the potential to rejuvenate stagnant agricultural sectors.
Secondly, with prudent management practices biomass production offers the opportunity to address multiple environmental concerns e.g.: land degradation, biodiversity, CO2 emissions, other GHG and acid rain pollutants, and local and regional health problems.
Thirdly, in developing countries and historically in industrialised countries biomass has traditionally been the only affordable energy source, often free, to the poorest sections of the community. Now, with the latest advances, both technical and socio-economic, biomass energy in conjunction with other renewable energy technologies is becoming economically competitive with fossil-fuel energy systems. It is interesting to note that whilst the costs of biomass energy technologies and feedstocks will continue to fall in real terms, {Ahmed, 1993; Elliott, 1993}, the costs of fossil fuel supplies and technologies are predicted to increase for the foreseeable future with the possible exception of coal {Williams, 1993; The Economist, Sept. 1993}
Nevertheless, before biofuels can emerge to occupy a significant segment of future energy supplies a number of constraints must be overcome. These include technical, social, economic and institutional problems; however, these constraints can be addressed given time and sufficient resources, (see below and section 6)
The growth of biomass supplies for energy production on a significant scale is both land and labour consuming. However, at the smaller scales relevant to rural communities in developing countries this is not necessarily the case since both food and fuel production can be integrated in complementary land use systems
In fact, at the small to medium scale (100 kW to 1 MW) sufficient amounts of energy can be provided from agricultural residues and non-arable land to supply villages energy needs for water pumping (domestic and irrigation), lighting and cooking. The provision of irrigation can greatly increase food and cash crop yields, implying that at this scale the use of indigenous biofuels can be land-neutral rather than consuming land resources. Furthermore, the production of excess biomass can be converted to higher value energy products e.g. charcoal or electricity, which can be sold on the open market. Firewood and charcoal are already significant income sources in rural areas.
At the larger MW scale, land use conflicts could occur where dedicated energy plantations are required to supply a central conversion facility i.e. where a market for biofuels is stimulated. Since biomass is a low energy density fuel high transport costs require that the conversion facility tries to secure supplies from as close to the plant as possible. Thus, measures to protect the small farmer near to such a plant may be necessary. Such measures may include guaranteed prices for any biomass supplies the small farmer might provide to the plant and anti-monopoly laws to avoid the conversion facility procuring all neighbouring land. However, such concerns must also be measured against the benefits accrued by such a plant i.e. increased rural employment (at all skill levels), a secure market for agricultural products and the provision of cheap indigenous supplies of energy.
The production of biofuels has the potential to have both positive and negative effects on all three major global environmental issues today, namely, land degradation, climate change and loss of biodiversity.
The extensive and increasing areas of degraded lands provide an opportunity for woody biomass species to be used economically for their rehabilitation. Whilst some of this land may have initially been degraded through the mining of indigenous wood resources often to supply urban charcoal markets, the establishment of multi-purpose bioenergy plantations can be a sustainable means of returning this land to productive use. Management strategies and policies required to provide the incentives for rehabilitation require resources to ensure future modes of land use are sustainable.
The sustainable production of biofuels and the use of present agricultural and forestry derived residues can play an important role in reducing the need for GHG and acid rain emitting fossil fuels. Sustainably grown biofuels are CO2-neutral and low in sulphur and the recycling of the ashes arising from combustion reduces the need for fertilisers. Wider revegetation programmes aimed at reabsorbing atmospheric CO2 may result in large quantities of low cost biomass being available which should be used as a substitute for fossil fuels or to produce long lived products.
In both industrialised and developing countries, close to source, biomass feedstocks can be competitive compared to fossil fuel feedstocks. Typically, biomass feedstocks can cost between $1 and $3 per GJ, which can be compared with oil costing roughly $2 per GJ at US$ 20 per barrel.{Hall et al. 1993} What has been missing, as succinctly put by Elliott {1993}, "is a conversion technology capable of delivering this energy to the market competitively on a modest scale appropriate to biomass." The ultimate high value energy carrier is electricity. Companies in industrialised countries are prepared to pay up to sevens times more per unit energy than electricity's alternatives because of its ease and versatility of use. Reliable and high efficiency technologies are now beginning to emerge which are capable of transforming biomass to electricity and other energy carries e.g. biogas, ethanol, at the correct scales (5 kW to 100 MW) to be economically competitive with equivalent fossil fuel derived energy carriers. {Ahmed, 1993; Elliott, 1993; Ravindranath, 1993}
Of particular interest is a GEF funded multi-national research project in NE Brazil aimed at the accelerated development of Biomass Gasifier Integrated Gas Turbines for the generation of electricity from dedicated tree plantations and sugarcane bagasse. With reliably estimated average sustainable wood feedstock costs of US$ 1.65 per GJ and projected capital costs for the gasifier and gas turbine module of about US$ 1,300 to 1,500 per 30 MWe unit, this system is expected to be competitive with future hydro-power generation projects and cheaper than present fossil fuel powered systems.
An important attribute of such biomass systems at the national planning level is the modular ability to add small increments of power generating capacity at a time thus minimising risk and reducing the capital investments relative to fossil fuel plants. This modularity will allow planners to follow the demand curve more accurately, thereby reducing the need for long term projections which are notoriously inaccurate and also increasing the reliability of the network at the same time.
Further important attribute of biomass energy systems is that with sufficient continuing research and development the cost of the biomass feedstock will continue to decrease. For example, in Brazil, since the inception of its sugarcane ethanol programme in 1975 costs of ethanol have been decreasing by 4% to 5% per year through increasing sugarcane productivity and decreasing ethanol production costs.
As a result of the site specific factors which affect biomass energy projects, constraints to the widespread uptake of biomass energy systems range from the local, to national, and regional levels. However, to a large extent enabling policies which remove constraints at the global/regional and national levels will have the most immediate effect. Such policies must engender the communication between the different institutions and governmental sectors involved with the establishment of a significant and sustainable biomass energy programme i.e. the agricultural, forestry, land planning and energy sectors. It is important to note that there are often no effective communication channels between these sectors/institutions which can represent a significant constraint to new biomass energy projects. {Williams, 1994}
Other important constraints include a lack of funding, the need for a "level playing field" for biomass energy, a lack of understanding of novel biomass energy technologies and therefore no backup or O&M facilities and above all a failure to appreciate fully the potential benefits which may result from significant bioenergy programmes.
