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Biomass is the largest source of energy from renewable sources. In 2001, biomass accounted for 3-4% of the total primary energy consumption within the European Union. Four of the 15 EU member states have bioenergy shares of more than 10%; Finland (16%), Sweden (14%), Portugal (13%), and Austria (11%). Much of this energy consists of heat production from wood, both for households and industrial processes. The contribution of biomass to electricity production is much smaller. Total electricity production from biomass fired power stations in the EU in 2000 was 37 TWh, or 1.5 % of total electricity production [EUROSTAT].

Biomass resources for electricity production are currently mainly agricultural residues (agricultural and forestry residues, manure and energy crops) and waste streams (municipal solid waste, industrial waste, sewage sludge and landfill gas).

Much of the existing resource is currently not used- partly because of barriers from technology and policy issues, and partly because it is not realistic to use the potential that is technically available. For example in agriculture it is not realistic to collect all biomass waste as much of this will have competing uses (as natural fertiliser) or cannot be collected easily from the many small resources. When looking at the potential of biomass, it is therefore important to take into account such practical limitations by defining a realistic potential.

The total realistic potential for biomass (excluding digestion) in the 15 EU countries is expected to be approximately 4200 PJ by 2010 [ECN 2003] growing to 5000 PJ per year by 2030 [ECN 2003a]. The countries with the largest potential are France, Spain, Italy and Germany, where especially the commercial production of energy crops are expected to make a substantial contribution in Spain and Italy. A likely distribution of biomass resources in 2030 is shown in the figure below [ECN 2003a].

Figure 1. Projected Biomass Resources Distribution in EU 15 in 2030

The potential for electricity produced from biomass digestion gases is estimated to be in the order of 5-10% of that of those fuels that combustion. Biomass digestion currently takes place mainly at landfill sites, where electricity production is not the main objective. In fact, 50% of all biomass digestion gas in Europe is currently flared off. Taking policies for landfill into account, countries with the largest biogas potential are Italy (sewage sludge and landfill gas), and the UK (landfill).

Biomass technology and projects in Europe

Combustion is the most widespread biomass conversion technology for energy purposes, primarily for heat generation. This typically takes the form of either combustion plants providing heat for a individual consumers or facilities supplying heat to district heating schemes.

Power generation from biomass combustion is usually steam based, i.e. utilising steam turbines for the conversion to mechanical energy. For this technology there are considerable cost savings with larger plants and it is usually applied only in relatively large plants. Frequently, it is operated as co-fired schemes, utilising biomass in combination with other fuels, for instance coal.

For power generation as well as co-generation schemes on a smaller scale, alternative routes are being pursued other than combustion and steam turbine combination. Usually, the objective is to convert solid biomass into fuels that can be used in engines or gas turbines.

Anaerobic digestion (AD)�i.e. production of biogas�has been applied for sewage treatment since the late 19th century, in Europe and elsewhere, though mostly in schemes giving low priority to the utilisation of the biogas generated for energy applications. AD�bacteriological decomposition of wet biomass in the absence of oxygen�is the most developed biochemical (or low-temperature) conversion process. Outside of Europe, AD has been extensively tested with several thousand plants having been built. The energy efficiency of these plants generally is relatively poor and furthermore they have a high failure rate. In Europe, the number of plants built is more limited and here the technology has had, and to some extent still has, substantial operational problems.

In the wake of the oil crises in the 1970s, there was a development and expansion of small-scale on-farm AD plants generating methane as energy source. In terms of number of plants. However, the expansion for Europe as a whole was much more limited than for instance in Southeast Asia, India and China, although the plants were typically working at higher energy efficiencies.

From the mid-1980s onwards, there was a new technological development trend based on centralised AD plants taking in feedstock from more than one farm and supplying heating via district heating schemes and power to the power grid. These plants are typically based on manure from farms, industrial waste and/or the organic fraction of municipal waste.

On this background, the AD plants vary substantially in size. According to a survey carried out in the late 1990s and published by AD-NETT (The Anaerobic Digestion Network, see the link www.ad-nett.org), there is the following rough distribution on size intervals:

� small-scale on-farm plants (a throughput of

� medium-scale schemes (100-1000 m3/day): approximately a quarter

� large-scale schemes (>1000 m3/day): approximately a quarter

As regard operating temperatures of the digester, there is a strong concentration among the European AD plants. More than 85% are operated at the mesophilic temperature range (25-40�C), 8% at thermophillic (55-70�C) and 5% at psychrophillic levels (5-15�C), according to the same survey. The majority of the thermophillic plants are in Denmark and to a smaller extent in Sweden. In Denmark they constitute the most significant fraction of the plants, both in terms of numbers and, even more so, when taking the plant sizes into account (the thermophillic temperature range is especially applied in centralised AD plants). Psychrophillic plants are primarily found in Italy, but even here they make up a minority of the total number of plants. A variety of basically different plant designs are being applied.

The product gas of the AD process is typically composed of about two-thirds methane and about one-third of carbon dioxide. In addition, there are small amounts of contaminants (notably hydrogen sulphide, H2S). To use the gas as engine fuel the carbon dioxide has to be removed, for which a variety of different methods exist. In addition, it is necessary to desulphurise the gas, i.e. to remove hydrogen sulphide, again using one of several techniques.

Besides AD, the most developed conversion processes from biomass to gaseous fuels can be categorised as thermochemical (or high-temperature) conversions. These are emerging technologies at an earlier development stage than AD. The most advanced principle is gasification - or partial oxidation - while fast pyrolysis has a longer time perspective and probably a higher degree of uncertainty.

There are a number of gasification demonstration plants in operation. There is a range of different plant configurations�updraft/downdraft, fixed bed/fluid bed, different fluid bed concepts�to choose from. The choice of configuration depends on the character of the feedstock used as well as the application of the gas. Updraft gasification, generally, have the best energy efficiency provided it is not necessary to purify the gas, which is necessary to utilise the gas in engines. On the other hand, updraft gasification is more versatile with respect to the feedstock (especially water content and ash melting point). In addition, the plant size is essential for the selection of plant design. Small-scale plants usually apply relatively simple fixed-bed configurations with correspondingly lower overall energy efficiency (electric efficiencies in the range of 15-25%). Such plants are typically in the range of a few hundred kilowatts and use gas engines. Fitted with gas turbines schemes in the lower megawatts range may achieve electric efficiencies in the range of 25-30%. In larger schemes�50-100 MW�more sophisticated technologies based on integrated pressurised gasification/combined cycle systems may reach electrical efficiencies of 40-50% or more. Above approximately 1 MW, only fluid bed configurations are being considered.

In the current gasification projects, the feedstock is almost exclusively wood. Also, straw has been investigated, but this option involves many problems.

Fast pyrolysis, i.e. thermal decomposition of biomass in the absence of oxygen, is a conversion technology at an earlier development stage than gasification. It is of particular interest in applications that can make use of the liquid fuels that may be produced by condensing the vapour gases generated in the process. The pyrolysis liquids may be used for both energy applications and to substitute chemicals.

In addition, pyrolysis may be an option in conjunction with feedstocks not well suited for gasification, such as straw and other feedstocks with high contents of chlorine and alkali. In pyrolysis at moderate temperatures, the chlorine and alkali content is retained in the charcoal. A demonstration project in Denmark is exploring this option.

Policy issues for biomass in Europe

Targets

The EU described its targets for renewable energy in the �EU White Paper on Renewable Energy Sources� published in 1997. The total (indicative) target is a 12% contribution of renewable energy to total energy consumption by 2010. Biomass is projected to contribute 135 Mtoe of the total projected 182 Mtoe in 2010, and is therefore expected to be the main resource for renewable energy. For electricity generation, the projected contribution of biomass is 230 TWh by 2010. Biomass will therefore also play a major role in electricity production from renewable resources, together with large and small hydropower (355 TWh and 55 TWh respectively), and wind energy (80 TWh). It is clear that these are ambitious targets. For biomass, much is still to be done in the coming years to grow from the current 33TWh (Eurostat 2002) to the projected 230TWh in the coming 7 years.

Following the White Paper, targets for electricity production from renewable energy sources were set in the Directive 2001/77/EC (October 2001). The total target is 22% of total electricity consumption in 2010. The (indicative) targets are set per country, and take into account resources available. For instance, the target for Austria is 78.1% (compared to 70% already in place in 1997), while that for Germany is 12.5% of gross national electricity consumption. This Directive will be one of the main driving forces behind renewable energy policy formulation in the EU countries in the coming years.

Policy support

One of the main policy issues concerning biomass is the definition of what to support under renewable energy policy, and what to regard as waste treatment issues. The definition of biomass formulated in the Directive is broad, covering not only the biodegradable fraction of products, waste and residues from agriculture, forestry and related industries, but also the biodegradable fraction of industrial and municipal waste. The definition of biomass in several member states however, exclude waste treatment (especially municipal solid waste) from support under renewable energy programmes.

For example in Germany, disagreements on the definition of �biomass� mainly concerning the utilisation of used wood (e.g. polluted by wood preservatives, etc.) and technologies led to insecurities for the development of the biomass sector. The 2001 regulation on biomass (Biomasse Verordnung) defines the different materials that may be regarded as "biomass" and the technologies for its utilisation, so resolving the former insecurities [IIP 2003]

Financial for biomass and biogas development is available throughout the EU, within the renewable energy policy. Policy support takes place through the available instruments, such as subsidies on investment, quota on the supply of renewable energy, or regulating minimum feed-in tariffs for renewable energy technologies. The levels of support differ substantially per country (for example feed-in premiums from 0.4 �cent/kWh to 14 �cent/kWh, with approximately 4 � cent/kWh as a common premium level). Production of electricity from landfill or combustion of waste is specified in a separate category in nearly all EU countries, receiving a lower level of support (commonly around 1.7 �cent/kWh). Less commercially viable technologies or projects such as small scale biomass digestors or electricity production from energy crops are commonly eligible for additional support, for example through research or demonstration programmes or a special high premium levels.

Biomass forms a special case within renewable energy policy, as it has stronger links with policy fields outside the energy sector than most other renewable energy technologies. For instance biomass use is strongly related to waste management and agricultural policy for the availability and cost of feedstock, to environmental policy for regulations on emissions (especially for biomass combustion) and disposal of process refuse. These linkages can form additional sources of support for the development and deployment of biomass energy technologies, but they can also form a barrier, especially through the existence of incoherent regulations in the different policy fields.

Regulations

As with many renewable energy technologies, the procedure to receive the necessary permits and certificates is commonly complex and requires a long time span. Related policy fields may further complicate the procedures. One major reason for the problems with regulations and procedures is the lack of coherency between different authorities involved at different levels (municipality, region) and for different policy fields (environment, spatial planning, energy). Such lack of coherency causes large delays and uncertainty for project developers. For example in The Netherlands, depending on the region, a farm scale biomass digester producing electricity may be classified as a power plant, and therefore not be allowed in rural areas.

Major influence on the utilisation of biomass for energy in the current and near future are the regulations on landfill or disposal of biomass waste on land. Illustrative with respect to landfill policy are Germany and the Netherlands, both anticipating a zero landfill policy. This means that electricity generation from landfill has no long-term potential for these countries, but electricity generation from combustion of biomass in (adapted) power plants may have larger potential. To indicate the complexity of the issue: combustion of biomass in power plants is currently most attractive in coal-fired plants, but for environmental reasons many of these plants will be closed down or be refitted to gas firing (which is more difficult to combine with biomass fuel).

In the future, regulations for land use for non-food production and agricultural policies are expected to be of major influence, as a large part of the growth of the biomass sector depends on the feasibility of growing crops especially for energy production (energy crops).

Concluding, the expansion of the biomass energy sector would be much helped if coherency is created between the policy fields and policy levels that impact the feedstock supply, permit procedures, and financial feasibility of projects. This is especially important for the biomass sector, as on the one hand the biomass sector is more complex than many other renewable energy technologies, and on the other hand the targets set for renewable energy in the EU depend largely on the growth of the utilisation of biomass for energy production.

References

AD-NETT (The Anaerobic Digestion Network), http://www.ad-nett.org/index.html, information downloaded January 2003

Al Seadi, T. & J. H. Nielsen, 2001, State of the art of biogas in Europe, BioEnergy 2001, Nordic & European Bioenergy Conference, Aarhus, Denmark, 25-28 September

Bridgwater, A. V. et al, 2002, A techno-economic comparison of power production by biomass fast pyrolysis with gasification and combustion, Renewable and Sustainable Energy Reviews, Vol. 6, No. 2, pp. 181-248

ECN (2003), Admire REBUS, ongoing research, database January 2003

ECN (2003a), BETER, ongoing research

European Commission (2001): Directive 2001/77/EC on the promotion of electricity produced from renewable energy sources in the internal electricity market

European Commission, Energy for the Future: Renewable Sources of Energy. White Paper for a Community Strategy and Action Plan, (COM(97)599 final)

Gunaseelan V. N., 1997, Anaerobic digestion of biomass for methane production: a review, Biomass & Bioenergy, Vol. 13, No. 1-2, pp. 83-114

IEA Bioenergy, 2001, Biogas and More! Systems and Markets Overview of Anaerobic digestion, Paris, France.

IEA Bioenergy, 2002, Thermal Gasification of Biomass, Paris, France

IIP, ECN, CIEMAT (2003-forthcoming), Green Independent Power Producers in Europe

UNDP, UN & WEC, 2000, World Energy Assessment. Energy and the challenge of sustainability, New York.