20-22 SB1009 Cover story 18/9/09 11:40 am Page 21
off, but most is used to produce electricity in
combined heat and power (CHP) engines at
OPINION
the sewage works. These units are inefficient
because they are small, and because there is
MAXINE PERELLA ON
usually no local need for most of the heat they
THE BARRIERS TO AD
produce; there is not much call for district
heating systems, for instance, because nobody AD actually makes much more sense
wants to live next door to a sludge farm. That for commercial food waste, because
makes the process only about 30% efficient of the volumes, rather than domestic
overall, meaning two thirds of the energy in food waste.
the sewage effectively goes up the chimney. Collecting little caddies of food waste
That level of inefficiency offends John from homes is not cost-effective for local
Baldwin of CNG Services to the core. As an authorities, and householders do not like
energy consultant, he argues passionately that it. That is the biggest barrier.
the best thing to do with biogas is inject it into You’ll see a lot of the big food retailers
the local gas mains, where it could be con- going for it though – M&S, Tesco, etc –
sumed in domestic boilers that are up to 90% but AD and MBT and other types of
efficient, or use it as transport fuel, particular- energy recovery (gasification, etc) plants
ly for lorries and buses, where good low-car- seem to be flavour of the month rather
bon alternatives are in short supply. “It’s a than incinerators, these days.
scandal to use biogas to make electricity when Maxine Perella is editor of
we can get around three times as much energy Local Authority Waste & Recycling
from the same volume of gas by putting it into
the gas grid,” says Baldwin. “There are lots of
other ways to generate green electricity, but ful incentive to process waste in ways that
very few for making renewable heat and trans- squander two-thirds of the potentially recov-
port fuel, so that’s how we should use it.” erable energy, and which reduce greenhouse
Injecting biogas into the gas grid (BtG) gas emissions by far less.
already happens routinely in Germany, An even bigger threat to the development of
Austria, the Netherlands, Sweden, and biogas in Britain is the continued construction
Switzerland, but has never been done in of large numbers of energy from waste (EFW)
Britain – until now. In June the water compa- plants – otherwise known as incinerators.
ny United Utilities and National Grid won These burn rubbish to produce electricity, but
£4.3M from Defra to fund a pilot project at the have major drawbacks. They are usually only
Davyhulme sewage works in Manchester 25% efficient, partly because there is seldom
using gas from an existing AD plant. Raw bio- any use for the waste heat; nobody wants to
gas, which is 65% methane, will be upgraded live next door to an incinerator any more than
into biomethane, which is 97% methane, the a sewage plant. Because incinerators are ineffi-
same concentration as natural gas in the mains. cient, and because much of the waste they
Some will be used to fuel 24 converted sludge burn is plastic, their fossil CO
2
emissions are a
lorries, and the rest injected into the gas mains third higher than those from a gas-fired power
to supply about 500 homes. station, according to a report produced by
If all the country’s organic waste resources Eunomia for Friends of the Earth.
were used for BtG, National Grid calculates it Worse, because incinerators require a steady
could supply about half the gas currently con- diet of hundreds of thousands of tonnes of
sumed in British homes. Combined with a waste a year, they tend to discourage councils
major improvement in home insulation, it from collecting food and garden waste sepa-
could be even more significant, says Johnny rately – the recommended policy of WRAP,
Johnstone, the National Grid manager the Government’s waste watchdog – and that
responsible for the Davyhulme pilot. “Biogas prevents further increases in recycling and
combined with increased energy efficiency has means less feedstock available for AD.
the potential to completely eliminate emis- In Sheffield, around 70% of municipal
sions from heating in the UK.” waste is incinerated and less than 30% recy-
But the playing field is tilted steeply against cled, and there are is no separate collection of
BtG by the subsidy regime. At the moment food waste. Nor is it likely in future, because
there is no subsidy for renewable heat, where- the city is producing less waste than originally
as renewable electricity attracts hefty subsidies forecast, and this shortfall means the contrac-
in the form of Renewable Obligation tor now wants to truck waste in from neigh-
Certificates (ROCs). Electricity generation bouring districts to keep the incinerator going.
from biogas gets two ROCs per megawatt In East Sussex, where the county council
hour, currently worth about £100 in total, has just won final planning approval for a con-
roughly double the market price of the elec- troversial 240,000 tonnes a year incinerator at
tricity itself. This gives a perverse but power- Newhaven, government funding is condition-
S Sustainable Business ❘ October 2009 21
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