Unlike a previous poster, on this subject, I have provided a link that ever one can use. Rather than omitting important information, I have high lighted some of the important aspects of biogas production.
Current production and future potential
The total annual biogas production in Sweden is almost 1.3 terrawatt hours (figures
from 2006). Several studies have concluded that the potential production in Sweden
is c. 10 times larger than this, or approximately 14 terawatt hours per year (Linné
and Jönsson, 2004). These calculations assume that c.10% of the agricultural land
can be used to grow crops for digestion in biogas plants.
If the possibility of
exploiting cellulose-rich woody materials (to produce so-called bio-methane) is also
considered (Held, 2007), the potential production of methane from native raw
materials increases to as much as 100 terawatt hours per year. Thus, the production
of bio-methane appears to be a realistic means of replacing a significant proportion
of the total annual consumption of fossil fuels in Sweden (90 terawatt hours).Large-scale biogas plants are now being planned, for example outside Malmö and
Stockholm. These plants, which will produce more than 50 gigawatt hours per year,
will significantly increase the total biogas production in the country. The
economies of scale associated with such large-scale plants will also improve the
competitiveness of biogas.
There is today a large unrealized potential to increase the production of biogas from
many sewage treatment plants that treat sludge derived from wastewater
purification. Many of these plants could produce more biogas if conditions were
optimised for the process (Mårtensson, 2007). An increased production of biogas
could therefore be realized with little investment and keeping costs to a reasonable
level, since these plants already exist.
Benefits
An increased use of biogas as a fuel reduces our dependence on oil, which has
important advantages both for the environment and for the security of our energy
supply in the long-term. Furthermore, the
biogas process plays an important role in
the recycling of nutrients between urban and rural areas and in the link between
consumption and production.A strategic energy and fuel resource
Sweden must free itself from its dependence on fossil resources to secure a future
supply of energy and fuel for industry and transportation. An increasing demand
for crude oil from remote and politically unstable regions is threatening the
security of our supply. Interruptions in the supply of fossil fuels threaten to further
drive up prices, which would reduce the competitiveness of Swedish industry. The
development of biogas represents a strategically important step away from oil
dependence which will contribute to a sustainable energy supply in the long-term.
Sustainable waste managementSustainable and efficient
management of organic wastes implies that the nutrients
these wastes contain (e.g. nitrogen, phosphorous and potassium) should be recycled
to productive land. From this point of view, organic wastes are an important
resource that can be exploited in a sustainable way. This also contributes to an
increased environmental awareness among those who source-sort their food waste.
Utilizing organic wastes in this way also reduces the amount that must be taken
care of in some other way, for example by combustion. With the help of the biogas
process, the production and consumption of food and energy from all sectors of
society can be included in a balanced re-circulation system. Integrated solutions for
water, energy and waste management will play an important role in the
development of sustainable urban areas.
Energy efficiency
One important factor to consider when arable land is used for the production of bioenergy
is the amount of energy obtained after subtracting the energy expended in
its production (i.e. the net energy production). The energy efficiency of growing
wheat for bio-fuel production was investigated in a study carried out at Lund
Technical University (Börjesson, 2004). The results showed that growing wheat on
arable land to produce
biogas is c. 3 times more efficient than growing wheat for
ethanol production.Energy can also be produced efficiently by combining ethanol and biogas
production. One example of this is the so-called Green gas plant at Norrköping,
which is run collaboratively by Agroetanol and Swedish Biogas. In this example,
ethanol is produced from wheat, while the residue by-product is used to produce
biogas by anaerobic digestion.
A thriving countryside
One of the advantages of biogas technology is that it can be established locally
without the need for long-distance transportation or import of raw materials. Small
or medium-sized companies and local authorities can establish biogas plants
anywhere (i.e. they need not be sited in any particular location, for example, in or
close to large cities).
Odour problems can be significantly reduced if manure is anaerobically digested
before being spread on the land. This can be a decisive factor in the survival of an
agricultural enterprise as an animal producer, especially if the land adjoins built-up
areas.
Cultivating crops for bio-energy on arable land is one way of maintaining land
within the agricultural sector. Surplus land (e.g. land that is today in ‘set-aside’)
otherwise runs the risk of eventually becoming overgrown. Biogas production
based on the cultivation of various agricultural crops thus maintains the potential
of the land to grow food crops in the future.
The profitability of agricultural enterprises can improve through the sale of
electricity and upgraded biogas, which means that more can survive to prevent the
re-forestation of the agricultural landscape. In turn, this will result in more job
opportunities and a thriving rural economy.
Clean fuel for industry
Methane is a fuel in demand by industry, partly because it is a gas, which gives a
high-quality combustion that can be precisely controlled. Methane burns with a
clean and pure flame, which means that boilers and other equipment are not
clogged by soot and cinders. This leads to a cleaner workplace environment and less
wear and tear on the plant. The methane molecule can also be used as a raw
material in many different manufacturing processes, with diverse final products
such as paints, plastics, furniture, animal feeds and lubricant oils.
Regional development and employment opportunities
The involvement of many interested parties in planning, construction, cost
estimation, administration and distribution is needed to ensure the successful
development of biogas as a vehicle fuel. In turn, this creates new job opportunities,
both locally and regionally. There are already several regional collaborative efforts
focused on biogas (Biogas West, Biogas South) and several more are planned (Biogas
East, Biogas North, Biogas Central). Promoting biogas also implies an investment in
job creation and regional development.
http://www.gasforeningen.se/upload/files/publikationer/rapporter/biogasinfo%20eng%202008%20sammansatt.pdf