ISIS Report 27/08/08
The Biogas Economy Arrives
The biogas economy is taking off, but will it mean vast swathes of energy
crops feeding enormous biogas plants instead of people? Dr.
Mae-Wan Ho
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referenced version of this article is posted on ISIS members’ website. Details
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Biogas Germany for Europe from “energy maize”
Only a few years ago, the ‘hydrogen economy’ [1, 2] was on everyone’s lips
as the natural successor to our fossil fuel dominated carbon economy. Not
anymore. A ‘biogas economy’ has emerged to take its place, at least for the
foreseeable future.
In 2007 the German Greens commissioned a report on the potential
of biogas in Europe from the Öko-Instituts
and the Institut für Energetik in Leipzig. The report, released to the media at the beginning
of 2008, claim that Germany alone can produce more biogas by 2020 than all of
EU’s current natural gas imports from Russia [3].
The biogas sector is booming in Germany and has
become Europe’s fastest growing renewable energy sector. The market leader
Shmack Biogas has received €130 million investment to expand its activities,
and is involved in several large scale projects. One of these is to build
Europe’s biggest biogas plant with E.ON Ruhrgas and E.ON Bayern;
it will be a 4 MW facility costing around €15.8 million [4]. After cleaning
and upgrading, the high quality methane will be fed into the natural gas grid.
Biogas production in Germany relies to a large extent on dedicated energy crops
such as maize, and has been a boon to the agricultural sector of the region
around Schwandorf. For the first time, farmers there are growing “energy maize”
crops guaranteed to be taken up by the biogas plant. Schmack Biogas’s announcement
in July 2007 made the unsubstantiated claim that energy maize “reduced the
land needed to grow feedstock by up to a third” and can “restore degraded
land and increase its fertility”. It did not foresee the huge increases in
food prices a year later due to the diversion of grains into producing energy
[5] (Food Without Fossil
Fuels Now, SiS 38), as a World
Bank report has recently confirmed [6].
Biogas is produced in anaerobic digestion of organic
wastes by communities of bacteria that are naturally found in livestock manure,
and consists of 60 to 70 percent methane, which can be used as fuel like natural
gas (see Biogas China
[7], SiS 32).. While it is
true that biogas is produced much more efficiently from crops - a hectare
of maize yields twice as much biogas energy than ethanol – its chief advantage
is that it can be produced from a wide variety of organic wastes such as livestock
manure, crop residues, food and food processing wastes, even paper and human
manure, and in a distributed, decentralized way to increase energy
efficiency in combined heat and power generation.
We have been promoting anaerobic digestion in ISIS since 2005, for mitigating
greenhouse gas (GHG) emissions and providing food and fuel security in the worsening
‘peak oil’ crisis [8, 9] (see Which
Energy? and Food Futures Now *Organic *Sustainable
*Fossil Fuel Free , ISIS publications). So we are naturally pleased that
the biogas economy is arriving.
The danger, however, is that the biogas economy will
be hijacked by big companies for centralised power-generation from bio-energy
crops, which may well jeopardise our food security and prevent its full energy
and carbon mitigating potentials and other benefits from being realised.
Biogas USA
A sure sign that the biogas economy will take off is that the United States
is talking about it too. A new study backs up the advantages of biogas from
livestock manure.
The US livestock industry produces more than one billion tons
of manure each year, most of it kept in lagoons or stored outdoors to decompose,
polluting the land, water and air, and emitting an estimated 51 to 118 million
metric tonnes of carbon dioxide equivalent (CO2e) in methane and
nitrous oxide, strong GHGs with global warming potentials of 21 and 310 respectively.
(One metric tonne, or 1 000 kg, is equal to 1.102 US ton).
Chemical engineers Amanda Cuéllar and Michael Webber at the University
of Texas, Austin, have taken a ‘top down approach’ and compared two scenarios
for their combined energy and GHG emissions [10]. Scenario A is business as
usual (Fig. 1, top panel), manure is left in a lagoon or in the open and coal
is burnt to produce electricity. GHGs are emitted both from the manure and
coal fire. Scenario B treats all the livestock manure in anaerobic digesters,
which converts the wastes into biogas (Fig. 1, bottom panel). The resulting
biogas is burned to generate electricity to offset coal-fired power, so the
carbon dioxide from burning biogas is the only GHG emitted.
Figure 1. How anaerobic digestion
of livestock manure saves energy and carbon emissions (see text)
Summing up all the manure contributions from the different kinds
of livestock, Cuéllar and Webber found a total of 928 trillion British Thermal
Unit (BTU) of energy available, which is about 1 percent of the country’s
energy use. And assuming biogas-fired power plants range in efficiency from
25 to 40 percent, between 68 and 108.8 billion kWh of electricity could be
generated each year, about 1.8 to 2.9 percent of the country’s electricity.
They then worked out the equivalent amount of coal that has to
be burnt to generate the same amount of electricity at a typical efficiency
of 33 percent for coal-fired plants, and compared the carbon dioxide emissions.
Biogas from livestock manure represents a saving of between 47.2 and 150.4
Mt of CO2, i.e., about 1.9 to 6 percent of the country’s carbon
dioxide emissions.
The US researchers have understated the case for biogas in many
ways. Notably, co-digestion of other organic wastes will at least double,
if not triple, the volume of biogas available, and because biogas methane
can be purified as a renewable fuel for mobile uses for cars as well as farm
machinery [7-9], it can displace larger amounts of fossil fuels, thereby contributing
even more to mitigating GHGs and saving energy.
Biogas Sweden
Sweden has led the world in biogas use for buses and other vehicles since
1996 [11]. Biogas methane has to be cleaned and upgraded for vehicles to avoid
corrosion and mechanical wear, and to meet quality requirements. Cleaning
involves removing particles, traces of water and hydrogen sulphide. Upgrading
involves removing carbon dioxide that makes up 30 to 40 percent of biogas.
Cleaning and upgrading are done to a standard set in Sweden in 1999.
The most common method of upgrading is scrubbing with water under
high pressure, the second most common method is Pressure Swing Adsorption:
CO2 is adsorbed on activated carbon at high pressure and released
when the pressure is reduced down to vacuum Other methods are adsorption with
organic solvents such as polyethylene glycol or a proprietary amine.
During 2006, 54 percent of the gas delivered to vehicles was
biogas. By June 2007, there were 12 000 vehicles driving on upgraded biogas/natural
gas and the forecast predicts 500 filling stations and 70 000 vehicles by
2010 [12].
The sale of biogas for vehicles is increasing every year; it
went up by 48 percent between 2005 and 2006, and by the end of 2006, there
were 95 filling stations for biogas/natural gas.
The use of biogas as vehicle fuel in Sweden started in the 1990s
by municipalities or companies owned by municipalities. They saw the biogas
generated at sewage treatment plants as a resource and a locally produced
renewable fuel. Municipalities still play an important role as the majority
of gas in Sweden comes from sewage treatment plants or municipal waste handling
companies. Private companies have now stepped in to sell vehicle fuel and
building filling stations. Energy companies like E.On Gas and Gothenburg Energy
have invested in upgrading plants and actively working for more renewable
gas.
Strong government support is important, it includes 30 percent
investment support, zero tax, reduced income tax for company car users, and
no congestion fees in the capital city of Stockholm.
If biogas can be injected into the gas grid (originally built
to transport natural gas) then all of the gas from the biogas plants can be
used. This would especially benefit small to medium scale biogas digesters
sited on farms. Rather like the electricity grid for distributed generation
from solar panels [13] (Solar Power to the Masses,
SiS 39), the gas grid also works as a backup and biogas can reach new
customers. In Sweden, there is only natural gas in the western part of the
country and so far, four biogas plants inject biogas into the grid.
Biogas Europe
In fact, many countries in Europe that have not yet gone
into anaerobic digestion to produce biogas are predisposed to take
advantage of biogas. In Italy, for
example, cars running on natural gas or on both natural gas and petrol are
widespread. While on a study/lecture tour in Italy in July 2008, I
was driven in a 17 year old 2 000 cc Audi that has been modified to run on
either petrol or methane. By simply pushing a button next to the steering
wheel, you can switch from one to the other smoothly while on the road.
The modification cost €700 and involved a
tank for compressed methane in the boot, with a capacity of 11 m3,
plus a ‘lung’, presumably a fuel-injection system for gas. Filling stations
for methane are every 25 km on ordinary roads, though not on the motorway.
The old Audi gave about 30 km per m3 of methane containing
about 40 MJ of energy, some 20 percent more than a litre of petrol. But methane
appears to run the engine a bit more efficiently. Methane was selling at about
€0.95 per m3, and petrol at €1.50 or more a litre. For the same
distance, it cost only 35 percent as much on methane as on petrol. No wonder
people were all filling up on methane rather than diesel or petrol. Needless
to say, as the price of petrol and diesel goes up, so does the price of natural
gas; which is another reason to use biogas methane as fuel.
Germany and Austria also have cars already running on natural
gas, and have both gone into biogas enthusiastically, though mostly using
bio-energy crops as feedstock. They recently set up national targets of 20
percent biogas in the gas sold to vehicles.
At the end of 2006, Germany had about 3 500 biogas plants with
total electric capacity of 1.1 GW in operation [12]. Most of the new biogas
plants have an electrical capacity between 400 – 800 kW. The first industrial
biogas energy park, Klarsee, with 40 biogas plants (total capacity 20 MW,
has come into operation. Energy crops are the main substrate, and manure constitutes
less than 50 percent. Industrial companies mainly built plants for fermentation
of energy crops. Germany is already growing energy crops on more than 1.3
million ha, or 11.4 percent of its arable land [14].
Currently, there are quite a few large biogas digesters at wastewater
treatment plants, landfill gas installations, and industrial bio-waste processing
facilities, and more are under construction (see above). But it has been predicted
[12] that by 2020, the largest volume of produced biogas will come from farms
and large co-digestion biogas plants, integrated into the farming and food-processing
structures.
How much biogas energy can we realistically expect for Europe
as a whole, counting both energy crops and livestock manure?
One estimate from the University of Southern Denmark [15] assumed
that energy crops convert to biogas at an efficiency of 80 percent, as not
all the compounds from biomass can be digested, for example lignin, and only
around 25 percent of the energy crop will be dedicated for biogas production,
the rest to be applied to other renewable energy production such as solid
and liquid biofuels. The EU27 has a total land area of 433.2 Mha, of which
196.6 Mha is agricultural and 113.5 Mha arable. If 20 percent of arable land
is dedicated to energy crops such as switch grass – so 5 percent goes to biogas
- 45.5 Mtoe (megatonne of oil equivalent) of methane can be produced at a
projected yield of 20 tonnes of solids/ha, about twice as high as currently
achievable.
In addition, the EU27 produces 1 578 Mt of cow and pig manure
a year. The animal production sector is responsible for 18 percent of the
GHG emissions, which includes 37 percent of the anthropogenic methane and
65 percent of anthropogenic nitrous oxide. The total potential for methane
from the livestock manure is 18.5 Mtoe.
Hence, a total of 64 Mtoe, or 71 200 million m3 of
methane can be produced by 2020 from energy crops grown on 5 percent of Europe’s
arable land, plus its mountains of livestock manure [15]. This does not quite
make up for the 74 400 million m3 of natural gas methane that EU
currently imports from Russia [16].
Obviously, if all the energy crops on 20 percent of EU-27’s arable
land were to be converted into biogas methane – which makes sense as it is
far more efficient than conversion into ethanol or biodiesel - the estimates
improve by quite a lot, as it would yield 182 Mtoe, giving a total of 200.5
Mtoe, about 10 percent of the current EU energy consumption of about 2 Gtoe
[17].
Natural gas consumption has increased in the last 30 years and
now accounts for almost one quarter of the world’s energy consumption. It
is projected to account for 43 percent by 2030. The theoretical potential
of biogas methane in EU27 would produce enough to supply 15.5 percent of the
natural gas consumption in Europe [15] (or considerably more if all energy
crops were dedicated to biogas methane production). At the same time, the
emissions of several toxic compounds like nitrogen oxides and reactive hydrocarbon
can be reduced by up to 80 percent compared to petrol and diesel.
A big question mark is whether dedicating 20 percent
of Europe’s arable land to producing energy crops is sustainable in terms of food
production and conservation of natural biodiversity. Practically all of the
set-aside land would have to be pressed into crop production.
The advantages of smaller scale local generation
None of the estimates based on energy crops
have taken into account the advantages of smaller scale local generation and
consumption [8, 9], which make energy crops unnecessary.
Biogas methane produced and used locally gives substantial energy
savings due to increased energy efficiency. The increase in efficiency could
be as much as 70 percent. That is because the ‘waste’ heat produced in generating
electricity can be retrieved for heating purposes, and local use of electricity
avoids the losses due to long distance transport through power lines. When
this is factored in, the energy and carbon mitigating potentials of biogas
methane simply from organic wastes, without any energy crops, can
be much greater, perhaps up to 50 percent or more in combination with organic
agriculture and localised food systems [9]. Add other small to micro-scale
renewable energies such as solar and wind, and we have no need for fossil
fuels altogether, let alone carbon capture and storage for big coal-fired
facilities [18] (Carbon Capture and Storage
A False Solution, SiS 39) or nuclear power [19] (Deconstructing the Nuclear Power Myths,
SiS 27).
A biogas circular economy operating at local levels
also gives us cleaner air and water, which is good for natural biodiversity
and the rural economy, and at the same time, provides rich organic fertilizers
for more abundant, nutritious, and healthier foods [9].
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