renewables – Made in Germany

162 biogas | industry overview
g Technology and
market overview
Biogas, produced by the fermentation of biomass, is
utilised worldwide to supply energy in various ways:
by burning it in combined heat and power plants for
power generation using waste heat (combined heat
and power, CHP), as biomethane fed into the natural
gas grid after appropriate processing of the biogas, as
fuel for natural gas vehicles or directly for cooking.
The German biogas industry has taken a pioneering
role in the field of generation and utilisation of
biogas. Germany is both the market and technology
leader, particularly in the area of gasification based
on organic waste and renewable sources. German
companies in the biogas industry cover the entire
value chain of biogas technology – from planning and
financing to the operation and maintenance of biogas
plants – and have many years of experience in process
biology and its associated laboratory services. Sophisticated
products are also available in the fields of combined
heat and power plants, storage and tank systems
as well as biogas analysis technology.
Technologies and applications
Biogas can be extracted from a variety of sources such
as organic waste from landfill sites (landfill gas),
municipal wastewater (sewage gas), and industrial /
domestic / commercial organic waste, as well as from
agricultural waste materials and energy crops. The
fermenting process of organic substances in an air-
and oxygen-free environment uses various anaerobic
bacteria, the composition of which depends on their
organic feed stock and specific process conditions
(temperature and pH level). A decisive factor in the
productivity of biogas plants are the microbiological
processes that occur during fermentation.
As a rule, agricultural biogas plants use liquid
manure �p 162 as a base material. Renewable
sources such as corn, cereal crops and other energy
plants such as sun flowers, Sudan grass, sugar beets,
oil radishes, sweet sorghum, etc., are increasingly
being used to increase gas yields. Commercial plants
also process waste water (from purification plants) as
well as waste from food production, food scraps,
grease traps and slaughterhouse waste. The extracted
g 90 % of the raw material for this biogas plant in Linne,
Germany, comes from liquid manure. After fermentation,
the digestate is used as high-quality fertiliser for fields.
f Cette installation de méthanisation à Linne, en Allemagne,
fonctionnera à 90 % avec du lisier. Après la fermentation,
les résidus de fermentation seront utilisés dans les champs,
comme engrais de haute qualité.
e Esta planta de biogás en Linne, Alemania, funciona en un
90 % con estiércol líquido. Tras la fermentación, los residuos
orgánicos se utilizan en el campo como fertilizantes de alta
calidad.
biogas is primarily a mix of 50 – 75 % methane and
25 – 45 % carbon dioxide as well as trace amounts of
water (2 – 7 %) and gases such as hydrogen sulphide,
oxygen, ammonia and hydrogen. Aside from the
biogas itself, a digestate is created – a mix of water,
minerals and organic substances, which have not
decomposed. This by-product can be used as a highgrade
fertiliser by farmers, thereby closing the nutrient
cycle with the cultivation of energy crops, or it can
be sold as mineral fertiliser.
The stationary use of biogas in combined heat
and power plants (CHP plants) for generating power
and heat �p 163 achieves a very high degree of efficiency.
The electricity produced can be fed into a public
grid or used as an independent power supply for
industrial and commercial areas, or even provide
power to remote rural settlements with no grid connection.
The waste heat can also be utilised in downstream
systems to generate additional power, for
heating and drying or in the operation of refrigerators.
In order to obtain higher power yields from CHP
plants, researchers are investigating the use of biogas
in fuel cells, which can convert the chemical energy of
BioConstruct GmbH