Biomass as an energy source Miscanthus yields more than energy
Fossil energy sources are limited and in combustion emit harmful greenhouse gases. This is why biomass is increasingly gaining importance as a source of energy for generating heat and electric power. Miscanthus, a perennial grass indigenous to East Asia, was hailed as a new bioenergy crop in the late 1980s. Failures in demonstration plots in Germany dampened the initial euphoria, but intense research has eliminated the problems, and miscanthus once again attracts attention for its outstanding qualities as a commercial energy source. Like maize, miscanthus possesses the C4 photosynthetic pathway. Unlike C3-plants, which make up the majority of plants, C4-plants show a remarkable combination of high light, water, and nitrogen use efficiencies. Miscanthus can grow up to 4 m tall and yields more biomass than any other plant in the world. Below-ground irrigation and fertilisation can increase the yield to 45 t dry weight per hectare and year. The energy yield is many times higher than the same area of a crop like rapeseed (biodiesel) could produce. Biomass can fuel local power generators. Another option is to use existing power-generating capacities and co-fire biomass with coal in traditionally coal-fired power plants. But miscanthus is more than an energy crop. Recent tests have proved its versatility, with end uses ranging from building materials, insulation and packaging material to composite materials and biodegradable synthetics.
Miscanthus x giganteus (Source: Dr. I. Lewandowski, Institut für Pflanzenbau und Grünland, University Hohenheim)
Manufacturers and suppliers
Factor-four effects
Ecological effects
Energy consumption Replacing fossil fuels with renewable raw material significantly reduces the consumption of limited energy sources. Miscanthus requires little energy input for infrastructure, fertilisers/pesticides and growing and processing.
Raw material consumption Use of non-renewable raw materials in miscanthus production and processing is limited to infrastructure and transport. Miscanthus requires significantly less fertiliser (phosphate, nitrogen, potassium, etc.) and pesticide input than other energy crops, e.g. grain, rapeseed, or sugar-beet.
Water consumption Miscanthus is a C4-plant that thrives on less water than other crops. Targeted below-ground irrigation via pipe systems increases yields.
Land use While mining fossil fuels entails large-scale interference in the landscape, establishing energy crops preserves rather than endangers landscapes. Miscanthus has the best energy per space ratio of all energy crops.
Waste Harvested miscanthus can be processed down to the last fibre, leaving no production waste. Ashes from combustion can re-enter the cycle as fertiliser.
Emissions and toxicity Renewable energy sources have a closed carbon cycle: The CO2 released while burning biomass is absorbed by the next crop growing. In contrast to fossil fuels like coal, petroleum and natural gas, the atmosphere is not polluted by additional greenhouse gas/CO2 emissions. The danger of water pollution by overfertilisation (nitrate, phosphate) is low. Compared to food production the pesticide input is extremely low, and miscanthus only requires pesticide input during the first and second year of establishment to keep out competing field plants. So far, no significant pests or diseases have affected miscanthus.
Transport and local availability The energy yield is not high enough to make transportation over long distances economically viable. This favours localised conversion and use at the place of availability, and the establishment of local infrastructure.
Natural materials and nature conservation Growing miscanthus has some advantages over conventional food agriculture. Perennials offer more animal and plant kinds a habitat than e.g. maize could. The soil improves, and as miscanthus requires only a low fertiliser input, the danger of water pollution is low. Miscanthus stabilises soil threatened by erosion.
Reliable yields Fields planted with miscanthus produce annual yields over decades without harming the natural balance of soil and ground water. Economic effects
Costs Growing and converting miscanthus as an energy crop is highly cost-effective.
Jobs and markets The conversion of biomass to biogenic solid fuels is labour-intensive and creates jobs. Growing miscanthus offers farmers an additional foothold, and a new professional profile is taking shape in the energy- and raw materials farmer. New employment opportunities benefit economically weak areas.
Availability and handling Miscanthus can be harvested with existing machinery (maize harvester). Biomass fuels are easy to store, even for longer periods of time, which ensures year-round availability.
Social effects
Health and safety Up-to-date conversion facilities pose no health risks. Appropriate handling will prevent the development of hazardous fungus spores or toxins that is possible in biofuel storage.
Obstacles and drawbacks The commercial exploitation of energy crops to a large extent depends on political framework conditions. Energy crops compete with other agricultural land uses. Conversion of land to residential or industrial uses, extensive organic farming and nature conservation conflict with other land uses. Targeted measures are necessary to make the establishment of miscanthus attractive for farmers. Though recent years have brought rapid progress, there is still scope for improving biofuel exploitation methods. Highly efficient methods to generate electricity are biomass gasification and combustion in gas turbines and fuel cells, both of which, however, are still under development. An infrastructure of local biomass power-generators with all the initial investment this entails is needed to use energy crops efficiently. Biomass combustion can only be cost-effective if prices make it a viable alternative to fossil fuels. Conversion of miscanthus into energy competes with its use as a material, e.g. in building. Using biomass as a material could turn out to be more cost-effective and environmentally sensible than using it as an energy source. Wood waste competes with fuel-oriented biomass farming. The costs of installing pipe systems for below-ground irrigation and fertilisation have not yet been evaluated. Large-scale miscanthus farming changes the landscape. Evaluating the ecological risks of farming a non-indigenous plant in central European ecosystems requires a longer period of observation. Removing the roots to switch back from miscanthus to other crops is rather laborious.
Potential Biomass currently makes up 3 percent of the total of primary energy used in the European Union, and only 1 percent in Germany. The EU commission estimates that by 2010, the share of biomass sources in renewable energies can increase to approx. 8.5 percent of the forecast total energy consumption in Europe. The share of energy crops in the primary energy demand is estimated at 1.7 percent. Their importance in the energy mix is expected to grow. As part of the EU programme for land set-aside, currently 6 million hectares have been taken out of food production and could be used for energy crops. Compared to other energy crops, miscanthus has obvious advantages. Its versatility promotes the development of breeding-, growing- and processing methods. New growth markets and job opportunities open up in economically weak areas.
Policy recommendations Energy and agricultural policy should establish a binding framework that guarantees long-term planning security and thus encourages investment in energy crop farming and processing. Standards for biomass fuels secure quality and promote trade. Legal obstacles need to be eliminated. Regulations for sludge treatment should permit the application of harmless ashes to the land as fertiliser. Internalising the external cost of fossil fuels and nuclear energy results in "real" prices and widens the scope for biomass on the energy market. The professional profile "energy- and raw material farmer" should be promoted.
Expert advice
For questions on FACTOR FOUR please contact: Dr. Raimund Bleischwitz Tel. +49-(0)202-2492-256 [email protected]
