Memorandum submitted by Jon Letcher (Waste
36)
The main subject of this submission is section
8—"the promotion of anaerobic digestion for agricultural
and food waste."
Relevant experience/interest: I am no longer
involved in digesters, but for nearly ten years I played a key
role in the promotion of Britain's farm digester industry, during
its most active phase in the 1980's and early 1990's—as
marketing manager of Farm Gas Ltd, and as co-founder and managing
director of Waste Refineries International Ltd. These two specialist
companies built virtually all the successful farm digesters in
Britain, treating many types of farm and other wastes; and WRI
won the RSA Better Environment Award for Industry (Product Category)
in 1991, for its work with digester by-products.
EXECUTIVE SUMMARY
1. Existing measures will encourage some
large, progressive farms to install digesters, but every livestock
farm in the country will need access to anaerobic digestion, if
the problems caused by livestock waste are to be solved; and only
a major government-funded digester building programme will have
any substantial impact on the problem.
2. However, such a programme could be financed
largely by loans which would be repaid out of farm savings and
income generated by the process. Digestion and separation reduces
the costs and problems of handling and storing slurry, and converts
it into three useful by-products—a nutrient-rich liquor
and a compost fibre, as well as biogas.
3. Fertilizer and compost manufacturers should
be encouraged to become involved in the use and development of
the liquor and fibre, which have already proved their potential,
and could have a profound effect on their own markets in the future.
Net metering for electricity would encourage smaller farms to
generate electricity from biogas.
4. Digesters should be installed at all
major agricultural colleges, both to give young farmers experience
of the process, and to clarify through research and trial programmes
the financial value and best practice in using the system and
its by-products. Maximising (and publicising) the benefits and
returns will encourage farmers to install digesters, and help
make the programme financially self-supporting.
5. On-farm co-digestion of farm with other
wastes such as source separated municipal waste and sludge from
small local sewage works could have considerable financial and
environmental benefits for waste managers, and create gate fees
which would attract many farms to install digesters, once the
planning and monitoring issues are resolved.
6. In the past, the narrow fields of interest
of different government departments caused the value of the process
to be seriously underestimated, which was one of the main reasons
why the UK's farm digester industry—then the most advanced
in the world—collapsed in 1994. A positive, co-ordinated
approach will be essential for success.
MAIN TEXT
1.1 Energy-related initiatives by the government
and by organisations such as Marks and Spencer will encourage
some farmers to install digesters; but there are many thousands
of livestock farms in the country which are all currently adding
to greenhouse gas emissions and other environmental problems.
1.2 Most of these are small, often hard-pressed
concerns which have neither the time nor resources to consider
side-issues such as power generation, though they may well be
very interested in the other benefits of the process, such as
reduced fertilizer costs and reduced waste management problems,
which affect the fundamental, everyday activities of their business.
Even 15 years ago many farmers were aware of the benefits of the
process, and believed that a digester must one day form an integral
part of every livestock farm.
1.3 But effective waste management is a
major investment for an average farm, and funding has always been
the key issue. Most of my own work within Farm Gas and WRI involved
helping farms to justify the cost of their digesters; and when
the 50% capital grant system was axed in 1994, WRI's hard-won
list of "potential imminent orders" fell in value almost
overnight from over a million pounds to zero.
1.4 If digesters are to be installed in
large enough numbers to have a significant effect on the problem,
and if we are going to make up for lost time—Germany already
has over 3,000 farm digesters in operation—a major government-funded
digester building programme will be needed. But the cost of such
a programme could be very modest, compared with that of many other
energy technologies.
2.1 In 1994 WRI was working on a proposal
for replacing the farm waste management grant scheme with a new
system based on loans—flexible, controllable and ultimately
self-financing, this system could still offer the best way forward
for the industry.
2.2 Our proposal—which seems very
small-scale now, but would have made a huge difference at the
time—was essentially that 50 farm digesters (costing about
£5 million in total) should be funded each year over a ten-year
period through low interest loans, which would be repaid by the
farms out of savings and income generated by the digestion/ separation
process.
2.3 The repayments from the first farms
involved would be used to help fund other "waves" of
installations; so by the end of a 10-year period 500 farm digesters
would be operating, and a permanent "rolling" fund established
which could, in time, fund the building of a digester on every
suitable farm in Britain, for a total public outlay (spread over
10 years) of about £50 million.
2.4 Costs have risen since then, but rising
energy prices and economies of scale would help redress the balance;
and although the scale of the programme would need to be greatly
increased in order to make a serious impact, the cost of even
a radically expanded programme would still be fairly modest, considering
the benefits involved.
2.5 The scale of the repayments could be
varied according to the uptake at any one time—during the
first year or two, for instance, to get the programme off to a
flying start, 0% interest with a repayment holiday might be offered
to a given number of applicants; but once the scheme was well
established, and the likely level of returns demonstrated in practice,
repayments could be stepped up, to build up the "rolling"
loan fund.
2.6 Large retailers such as Sainsbury's,
which have banking interests as well as being the major outlets
for many farms likely to involved in the programme, may find a
marketing advantage in helping to create the loan fund in the
early stages—by launching a special account for their customers,
perhaps—to get the programme off to a flying start.
2.7 Renewable energy contracts would be
the simplest means of regulating the returns for the farms initially,
but as the value of the other by-products and on-farm cost savings
became better established, these could play an increasingly important
part.
3.1 In the early 1990's, the digested separated
fibre was a key part of our marketing strategy for digesters,
and by varying the rates at which we contracted to buy back the
fibre from our digester customers we were able to control—to
some extent—our flow of digester orders.
3.2 To make this possible, we developed
our award-winning "Heritage" range of peat-free composts,
based on digested composted manures, coir and wood waste, which
included a seed and potting compost (trialed by Pershore Horticultural
College) as well as simpler landscaping products such as soil
conditioner and tree planting compost.
3.3 As a small producer, developing a brand
new product range from novel materials, it was always a struggle
for us to compete with the big established companies, such as
Fisons, and we would have preferred to sell the fibre to them,
to use in their own peat-free or low-peat products, so that we
could concentrate on building digesters; but the volume of digested
fibre was too small to interest them at that time. If hundreds
of farm digesters were being built every year, the situation would
be different, and although the very low prices of peat-based compost
products at present mean that the fibre would have little impact
on the returns from farm digesters initially, the high quality
of the material, and the large volumes involved, mean that this
fibre could become important in the future, as peat stocks become
ever more depleted.
3.4 The fibre's high nutrient content—which
makes it attractive as a soil conditioner—means that it
has less value as a substitute for peat in growing media; but
one of our experiments revealed that the salts content was greatly
reduced by the leaching effect of rainwater over a single winter
(the runoff was stored with slurry for use as liquid fertilizer),
suggesting exciting possibilities for the future.
3.5 Reducing the use of peat would also
help to reduce greenhouse gas emissions; as would—potentially
to a much greater extent—savings in the use of artificial
fertilizers.
3.6 Digestion and separation make the nutrients
in slurry more readily available as a fertilizer, both by altering
the chemical form of the nitrogen, and by converting the thick,
unmanageable slurry into a thin liquid which can be easily analysed
for its nutrient content, and spread in a controlled way by irrigator;
and some livestock farmers with digesters reported savings in
fertilizer costs of 70%.
3.7 Paragraph 3.7 not printed.
3.8 Paragraph 3.8 not printed.
3.9 In the future, it is possible that the
use of digesters could radically alter the whole concept and practice
of fertilizer use and application on livestock farms.
3.10 Reducing the total nutrient loading,
by making full use of the nutrients in slurry, can also help reduce
nutrient pollution of ground and surface water.
4.1 As part of WRI's strategy for promoting
farm digesters, we installed a digester system at Walford College
of Agriculture in Shropshire, in the early 1990's, which is still
operating today.
4.2 The system included a compost making
unit and CHP generator; and we also planned that the college would
conduct trials into the fertilizer value of the liquid, though
these trials never took place on the scale originally intended.
4.3 As part of a digester building programme,
comprehensive systems similar to the one we built for Walford
should be installed on all key agricultural colleges, and trials
into the fertilizer value of the liquor, and potential savings
in waste management costs, should be carried out as soon as possible,
preferably working in conjunction with independent on-farm trials,
such as those currently planned for the island of Westray in Orkney.
4.5 But it is essential that trials should
not be allowed to delay the start of the farm digester building
programme itself. AD is a fully developed process, used on sewage
works for over a hundred years; and Farm Gas and WRI have between
them successfully treated virtually every type of livestock waste.
(Incidentally, all these projects were the work of my former colleague
James Murcott, now of Methanogen, the co-founder of both Farm
Gas and WRI Ltd; who is not only by far the most experienced and
successful farm digester engineer in Britain, but has been the
industry's leading light for 25 years, and the first to fully
appreciate the importance of the liquor and fibre, and of on-farm
co-digestion; and I strongly recommend that you call him as a
witness for your enquiry.)
4.6 There is no need for more demonstration
projects, which can be expensive, self-propagating, and can give
misleading results, as the capital and running costs of these
high-specification units can be much higher than those of standard
on-farm systems.
5.1 Treating sewage sludge in rural areas
and smaller towns can be a problem, as the sludge must either
be transported, after primary treatment, to a centralised processing
plant, and transported away again for disposal, or a suitable
on-site treatment system must be installed, incurring high capital
and maintenance costs.
5.2 On-farm co-digestion with farm wastes
can reduce costs for water companies and their customers, reduce
the amounts of fossil fuel used for sludge transport, and provide
valuable gate-fees for the farms involved.
5.3 The costs of transporting and spreading
the sludge can often be greatly reduced, as the sludge, after
treatment, is spread with the farm slurry by irrigator, while
the capital cost of the extra digester volume required for the
sludge is minimal (1 cubic metre of digester volume, which will
treat the waste from only 1 dairy cow, will process the sludge
from 100 people.)
5.4 We discussed projects of this kind with
several water authorities, and some operating managers were very
interested; but the projects came to nothing mainly because of
the lack of a co-ordinated plan for setting and monitoring standards,
relative to environmental, health and planning issues. If these
issues were resolved, co-digestion could help many farms to afford
the cost of a digester.
5.5 The same is true of other wastes, especially
organic wastes from source-separated domestic rubbish; and I believe
that on-farm co-digestion of these materials with livestock wastes
would often prove to be a preferable and more practical route
than installing digesters purely for domestic waste processing
alone.
6.1 In the past the industry has suffered
by falling between a number of departmental stools.
6.2 To avoid these problems in the future,
I believe a biogas programme should be made the responsibility
of a single programme director, who is not involved in any other
form of energy or other project, and who reports to and is supported
by a panel of representatives of the relevant government departments,
farmers, digester manufacturers, and (once the programme had gained
momentum) those involved in the use of the by-products.
6.3 This director must be given authority
to negotiate and hopefully resolve at a national level such potential
barriers as the planning and monitoring issues involved in co-digestion
schemes, and to co-ordinate the research projects mentioned above;
but his main responsibility should be to ensure that the required
number of digesters is installed, week by week.
6.4 I am confident that, if the government
committed sufficient funds in the early stages, a major biogas
programme could be initiated quickly and successfully—a
clear commitment by the government will attract investors and
manufacturers, who will promote the process actively by the usual
channels.
6.5 I have given many talks about the process
in the past, including a series organised by the Wildfowl and
Wetlands Trust, and I am sure that a farm digester programme would
be strongly supported by the general public, especially as it
would arouse none of the controversy surrounding some other forms
of renewable energy.
6.6 It would also help dispel the myth that
such technologies are bad for the economy. A farm digester programme,
in addition to its environmental benefits, could substantially
improve farm incomes, and create a major new industry for rural
areas—WRI's staff of 25 were building about one farm plant
per month, and there are at least 30,000 farms in Britain that
need access to a digester.
Jonathan Letcher
November 2007
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