Anaerobic Digestion Can Be Best Overall Including Being Cheapest Overall

I guess that if you are a long term subscriber this headline will not be a surprise, but it is good to report that others think so too! Read on and find out why.

Processing food waste using anaerobic digestion technology is not necessarily as expensive in relative terms as some councils may think, consultancy Eunomia has claimed.

Speaking at the AD In the City event held in the UK by BiogenGreenfinch last month, senior consultant, Dr Adrian Gibbs, said that using AD to process food waste collected separately could work out cheaper than processing commingled food and green waste together in an in vessel composting plant.

Dr Gibbs explained that a report by Eunomia had found that sending food waste to AD and green waste to windrow composting cost UK councils £9.50 in gate fees per household per year, whereas sending commingled green and food waste to IVC cost £10.80 per household. He also said that just collecting food waste alone and sending it to AD cost £5.50 per household over the same period.

Dr Gibbs admitted that average gate fees for AD facilities - around £55 per tonne - were higher than IVC - which, he quoted as £45 per tonne, but said that "overall AD is cheaper". He also claimed that separate food waste collections also worked out cheaper than mixed collections and said that the number of local authorities which were implementing separate collections had risen from 11 in 2007 to 54 in 2008.

He told the London borough council officers who attended the event, which was set up to explore ways to introduce more AD capacity in London, that - "AD is better than IVC, it's the way to go and it is the one I would watch."

Anaerobic digestion treats food waste in an oxygen-free environment and produces biogas - which can be converted into energy - and a nutrient rich digestate which can be used on farmland. It also has the potential to provide combined heat and power (CHP).

IVC treats green and/or food waste and sometimes card in an enclosed but oxygenated and aerated environment and produces compost. It does not generate energy.

A number of strengths and weaknesses were highlighted for both separate and mixed collection. The plus side to mixed collections included - only needing to use one vehicle, only one bin required and quick and cheap collections.

However, Dr Gibbs explained that the seasons significantly affected what was collected, with garden waste levels dropping significantly in the winter, meaning that feedstock was inconsistent. He also said that the waste had to be processed in an enclosed environment due to Animal By-Product Regulations and this ups the cost of green waste.

Dr Gibbs also pointed out that green waste and food wastes required different collection frequencies. In addition, not all homes have gardens and collecting green and food waste together prevented councils charging for green waste collection. He claimed that separate AD collection reduced net costs for councils and allowed local authorities to charge for garden waste. He added that there is a large quantity of food waste which could potentially be picked up.

Dr Gibbs said AD had a number of strengths, including -

* Internationally proven technology
* Anaerobic Digestion has strong government support in the form of ROCs, a Task Group and feed-in tariffs
* It is a carbon positive technology
* Valuable outputs - biogas and digestate - and
* Leaves green waste to go through the cheaper windrow process.

He said Anaerobic Digestion's only weakness was the lack of facilities in the UK, adding - "AD wins hands-down for organic waste."

Reflecting On UK Anaerobic Digestion Policy to Start the New Year

The Christmas and New Year period allows a little more time than usual to reflect on the path that we are treading in the UK, and many other EU nations as well, toward greater utilisation of AD and organic waste in the quest to divert waste from landfill.

Also, by using biogas we will both be gaining renewable energy from an otherwise wasted resource, and avoiding the emission of methane which is such a potent greenhouse gas and we will at least move in the right direction toward sustainability.

Also, there are opportunities via carbon credit funding for EU companies to buy CERs from developing nations, thus enabling them to utilise AD and similar sustainable processes.

I think that what I am describing was in fact very well stated by Dr Stephen Etheridge*, as Chair of the UK Chartered Institution of Water and Environmental management, in his CIWEM Water & Environment Magazine, July/August 2006.

The following is an extract from that article:-

In the UK, around 31 million tonnes of MSW are produced annually. Approximately 30 percent of this waste is biodegradable. As a result of the EU Landfill Directive, the UK waste management authorities must divert the biodegradable fraction of MSW from landfill to other treatment options.
Based on experience from full-scale AD facilities for MSW in Europe, the use of AD technologies in the UK could contribute significantly to waste and renewable energy targets. In order to address this, Defra carried out a consultation in 2003 on the potential role of AD as a bioprocess that could meet energy and soil conditioner objectives for Best Value Performance Indicators (BVPI).

The consultation confirmed that if all the biodegradable MSW in the UK was used to generate biogas from digestion plants, approximately 2,420 million kilowatts of electricity could be produced each year.
As a result of the drive to combat climate change the emphasis in many parts of the world is now on mitigating emissions of methane to the atmosphere from existing treatment lagoons, landfills and other waste management systems. Methane is 23 times more potent than carbon dioxide as a greenhouse gas and for every tonne saved there is the potential to secure a tradable certificate of emissions reduction (CER) worth 23 tonnes of carbon dioxide, Under the Kyoto Protocol emissions reductions in developing nations can be purchased by developed countries as a way to cost-effectively reduce their obligation to reduce carbon emissions.

Since many developing countries are in warm climates where methane is readily generated, anaerobic digestion is an ideal technology to mitigate emissions and to capture the biogas for the production of a renewable energy. In addition, developed nations are keen to buy CERs to offset difficult targets which must be achieved at home.
In a recent study funded by the UK FCO (Foreign and Commonwealth Office) significant opportunities were identified for cattle, pig and agro-industrial operations in Mexico. To benefit from emissions trading opportunities each developing country must have a host nation office and a local infrastructure to certify emissions saved. These are now more prevalent and where they are not established many countries are in the process of doing so.
Although it is early days for CER trading, companies are already signing up potential clients in developing countries. Often the climate is naturally warm and with an appropriate low cost technology based on covered lagoons lined with flexible liner materials such as HDPE (high density polyethylene), digesters can be deployed to treat many agro-industrial wastes. The Asia BioGas Company has constructed nearly 50 anaerobic digesters in the last four to five years. One of these, based at a cassava factory, is thought to be the largest digester in the world.
Anaerobic Digestion is a unique technology which presents a range of opportunities to generate renewable energy, treat biodegradable MSW and reduce carbon emissions. It is precisely because the technology straddles different areas that incentives and support must be cross-sectoral. Whilst this has been implemented very successfully elsewhere in Europe, there are still challenges to be overcome in the UK if this technology is to achieve its true potential. ■
*Dr Stephen P Etheridge was the Chair of the CIWEM Scientific Group and a member of CIWEM's Waste Management Panel. He was co-Chair of the Environmental Protection Subject Group of the Institution of Chemical Engineers and Editor for Waste for the European Federation of Chemical Engineering. He has led a number of international projects in Asia and Europe in the environmental and renewable energy sectors and was recently appointed Chief Technology Officer for the Asia BioGas Company.

So, there it is, and we are now two and a half years further down this path and real progress has being made in the adoption of AD on a much wider scale than thought possible even in 2006.

Hopefully, 2009 will see energy prices returning to a viable level from recent lows of scarcely $50 per barrel, and the lending banks will return to being just that, and all before we see a derailment of this progress.

Wishing all our readers very best wishes for 2009.

(Oh! Yes! Before I forget! Please participate by commenting whenever possible on these posts throughout the New Year! We have over 400 subscribers to these posts. However, responses are so much appreciated otherwise your Blogger wonders whether anyone is actually reading these posts!)