Biogas is a gas produced from the treatment of organic compounds contained in biomass. It is a secondary source which results from the treatment of biomass with the use of various processes. The most common technology of biogas production is methane fermentation, where in anaerobic conditions, the physical and chemical processes with the support of methane bacteria decompose organic matter into gas.
Biogas is a combustible gas and it may be used as a fuel driving a gas turbine producing electricity, as a fuel used in a heat-producing boiler or, which is more frequent, as a fuel driving the engine of co-generation system, where electricity and heat are produced in one process. Biogas may be appropriately compressed after its purification and used as a fuel driving motor vehicles in transport. Such solutions are well known in Sweden, as well as in Germany or Austria.
Biogas may be used locally for energy purposes by coupling the generated fuel with a biogas-combusting unit or, after purification, it may be introduced to the gas network, transmitted and then used for energy purposes.
- The composition of biogas
The voluminal composition of biogas is strongly dependent on the type of biomass used to produce it. It is only composed of elements resulting from organic matter. Biogas (non-purified) consists of approx. 50 – 65% methane (CH4), 30 – 45% carbon dioxide (CO2) and other components in trace quantities such as steam (H2O), hydrogen sulphide (H2S), nitrogen (N2), hydrogen (H2), oxygen (O2).
- Biogas mass
Knowing the voluminal composition of biogas, it is possible to determine a rough approximation of its mass. In normal conditions (pressure and ambient temperature of 1013.25 hPa and 273.15 K respectively), the mass of biogas amounts to approx. 1.2 kg / m3.
- Calorific value
The calorific value of biogas directly results from the methane content in biogas. Typical biogas is characterised by calorific value of 19 to 23 MJ / m3. Knowing the calorific value and production of biogas, it is possible to determine the amount of primary energy generated in a given time unit, and then, taking into consideration the efficiency of the system converting the primary energy into the final energy, it is possible to determine the amount of electric and/or heat energy which may be produced. Assuming the conversion efficiency at the level which is reached by co-generation units (CHP) currently available on the market, approx. 2.2 kWh of electricity and at the same time approx. 8 MJ of heat may be produced from 1 m3 of biogas.
- Other biogas parameters
colourless, odourless, consists of a mixture of combustible and non-combustible gases; only methane results in energy gain.
The breakdown of biogases according to their types is symbolic and determined by the material (biomass) from which a specific biogas was produced. At present, the following types of biogases are distinguished:
- landfill gas
results from the decomposition of organic compounds within landfill sites
- sewage biogas
results from the decomposition of organic compounds from sewage residues
- municipal biogas
results from the decomposition of biodegradable organic compounds of municipal waste (e.g. leaves from parks).
- agricultural biogas
results from the decomposition of materials of agricultural origin.
The amendment to the Energy Law Act made by the legislator on 8th January 2010 introduced a definition of agricultural biogas determined as a gas fuel obtained in the process of methane fermentation from the following raw materials:
- agricultural raw materials,
- agricultural by-products,
- liquid or solid animal dung,
- food processing industry by-products or remains,
- forest biomass.
The definition refers to artificially introduced raw materials used in the production of biogas in the methane fermentation process, particularly when they also refer to forest biomass. Nevertheless only agricultural biogas stipulated by the above-mentioned definition was recognised as gas fuel, which enables its integration with gas network. This possibility has been existing since 1st January 2011, but only theoretically, because there is still no executive regulation to the act passed, which would determine the parameters of biogas (e.g. composition) required for introduction, the conditions of obtaining a connection to the gas distribution network and a support scheme of producers of agricultural biogas. According to the draft version of the regulation the possibility of forcing agricultural biogas into the network may depend on the adjustment of its parameters to the quality of gas already transported within the network.
A biogas plant or a power station using biogas?
Biogas plants, a biomethane plant, a biogas power plant, a biogas CHP plant, a bioelectric power station, biogas installations and many other names come up in connection with the development of this sector in Poland. However not every name is used correctly. This results from the fact that Polish regulations do not include any classification of this type of installations. One might, however, try to give certain names to specific installations:
biogas plant – an installation producing biogas
biogas CHP plant – an installation producing heat and power from biogas.
Adopting the above definitions, one might say that a biogas plant is an element of a biogas CHP plant.
Biogas plants functioning in Poland
The number of biogas plants in Poland at the end of 2010 reached 143, which translates into total installed electric capacity of 82.5 MW. It is not much taking into account the fact that according to the adopted strategic documents their number should reach in 2020 the capacity of 802 MWel (Polish Energy Policy) and 980 MWel (National Action Plan). The biogas installations which are currently in operation in Poland are used for the production of power or combined heat and power. The majority of installations use landfill or sewage biogas. Only 8 installations produce energy based on agricultural biogas (as at the end of 2010). In 2010 the share of power from all biogases in the balance of total power generated in renewable sources reached the level of approx. 3.5%.
The reason for the disproportion in installed capacities of individual biogas technologies is the support scheme for electricity from renewable sources adopted in Poland in 2005 as a result of Poland’s accession to the European Union and the necessity to implement Directive 2001/77/EC of the European Parliament and of the Council of 27th September 2001 on the promotion of electricity produced from renewable energy sources in the internal energy market. Poland adopted the system of so-called green certificates for supporting electricity from renewable sources, which equally promotes every entity of electricity irrespective of the renewable source or technology used. It means that an entrepreneur who produces 1 MWh of electricity from agricultural biogas will earn the same amount of revenue as an entrepreneur who produces is based on landfill or sewage biogas. Taking into account the fact that the raw material for the production of landfill or sewage biogas may be obtained practically without incurring any costs, agricultural biogas in Poland is not able to compete on the energy market with other types of biogas, taking into consideration the current conditions.
Barriers to the use and development of biogas
- The issue of using post-fermentation matter for fertilization of crops has not been regulated, even if the installation processes raw materials of agricultural origin only (plants and animal dung). It is necessary to carry out a number of tests before the matter may be used for fertilization. The issue of giving the post-fermentation matter to physical persons has also not been regulated.
There is no possibility to obtain a location decision over the course of a simplified procedure
- The construction of biogas plants and the distribution network are not included in the list of public purpose investments as defined by the Real Property Management Act of 21st August 1997.
- Very few communes have local plans of spatial development (miejscowy plan zagospodarowania przestrzennego, mpzp). A small area of towns in Poland is covered by mpzp (between a dozen and several dozen per cent); an even smaller area outside towns is covered by mpzp (up to several per cent). It rarely happens that mpzp takes into account renewable sources, and even more rarely biogas plants.
- If an investor is interested in locating a biogas plant on such areas, agricultural land should be transformed into areas for non-agricultural purposes. This fact is reflected in the local plan of spatial development. However it must be preceded by a consent and this involves additional costs, in particular for locating a biogas plant on land belonging to productivity classes 1 to 3.
- There is no guarantee /priority of connecting a biogas power plant to the power grid and biogas plants to the gas network. A complicated procedure of obtaining the so-called connection terms (advance, location decision before obtaining the connection terms). The waiting time for the connection terms after submitting a relevant application is long (up to 150 days, irrespective of the installation size).
Weak and unstable support system
- green certificates do not facilitate large-scale development of agricultural biogas plants. Their functioning is limited in time up to the year 2017, unless the draft Act on Renewable Energy Sources provides otherwise. Nevertheless, the value of a certificate at the current level does not guarantee the return of capital investment within a typical investment credit period amounting to 15 years.
- co-generation certificates will function until 2012 (the yellow ones) and until 2018 (the violet ones) only. The price of the purple certificates does not in any way encourage the investor to ensure that a co-generation unit is highly efficient, which constitutes a prerequisite for obtaining co-generation certificates. An amendment to the regulation on co-generation has still not been passed, and for that reason the support scheme of purple certificates is not functioning.
- brown certificates for an equivalent amount of electricity calculated on the basis of the amount of agricultural biogas forced into the gas network are still not functioning. The algorithm of converting biogas into an equivalent amount of electricity supported by brown certificates, puts biogas plants integrated with the gas network in a much worse position in terms of investment profitability than biogas combined heat and power stations, even those which are not highly efficient.
- organisational barriers: lack of technical and expert base, poor infrastructure of the gas network, of the grid, not mentioning the heat distribution network
- poor availability of information about the rules of operation of biogas plants, aversion of society to biogas investments.