R-Urban

R-Urban London

Blog

LEAP - Micro Anaerobic Digestion

Introduction

LEAP micro AD is a cross sector partnership developing micro anaerobic digestion, a renewable technology that turns all organic waste (except wood) into a clean fuel and fertiliser. The biogas produced can be used for heating, cooking and lighting or be cleaned and compressed for use as a vehicle fuel. The fertiliser is a valuable product with excellent levels of nitrogen, good for food growing and turf strengthening.

Seed foundations

Just as a pearl forms from a tiny grain of irritation, so the LEAP project evolved in response to a dissatisfaction. In 2011 Community by Design, the organisation who went on to found LEAP, realised their latest 3-year project was not sustainable. It relied on regular injections of funding to deliver its free health and wellbeing services to the community.

Previous projects followed similar lines, with the excitement of an initial concept leading to fundraising and subsequent realisation of the idea. However, missing in their design was an inbuilt ability to become economically sustainable, thus limiting benefits and autonomy.

Another concern arose; providing something for free can sometimes encourage reliance; how could we create something that generates concrete opportunities for people so they can sustain themselves? And while we’re at it, how can those benefits be mirrored in the environment, particularly those largely unsustainable arrangements we call cities?

These questions led to research into establishing a social enterprise to generate biodiesel from waste oil. Several months in, anaerobic digestion (AD) emerged as more promising technology around which multiple social, environmental and economic benefits could be woven.

Sending out roots

Networking played a large part in forming the LEAP partnership. Later in 2011, a 3-year pilot project exploring micro AD was reaching its culmination after having commissioned several reports and demonstrated the technology with a 0.6m3 digester in Newcastle.

Led by Cath Kibbler from the Community Composting Network (CCN), it had gathered substantial interest across the country, forming a Micro AD (mAD) steering group with members spanning engineering/manufacturing, public, academic and community sectors.

This blend of private, public and community interests informs LEAP, which comprises Community by Design, the Community Composting Network, several members of the mAD steering group including James Murcott and Angie Bywater from Methanogen, Guy Blanch (Alvan Blanch research engineer) and David Neylan PhD, plus a few new additions - Mark Walker and Davide Poggio from Leeds University and Aleka Designs.

First shoots

The partnership’s first funding application with Camden Council was successful, giving us a solid 2-year foundation upon which to build. Camden is known for its progressive approach to sustainability, which led to their installation in 2008 of the first biomethane refueling station in Europe, despite other countries having larger AD industries e.g. Germany’s 7000-8000 plants compared with the UK’s 100 plants. Biomethane burns cleaner and more quietly than petrol or diesel, significantly lowering PM10s ((particulates) and NOx (nitrogen oxides), the most harmful emissions for health.

Kicking off in April 2012, the project designing its first system building on CCN’s experience. While AD plants in the West are generally medium-high tech large-scale industrial affairs, developing countries actually have more m3 of digester capacity, with millions of low-tech micro plants in China, India, and Nepal.

Our challenge involved making micro AD cost effective in a colder climate where heating and mixing are required, and expectations of user friendliness, aesthetic design and regulatory compliance are generally higher.

Our initial system design addressed changing gas use across the seasons to include electricity and heat generation in winter and cooking and water heating during summer. It also featured feeding flexibility with a mill and pre-feed tank that could receive feedstock (organic waste) and pump it ready macerated and mixed into the digester at regular daily intervals.

Regularity is important, as the digester is essentially like a stomach where microorganisms break down organic matter in the absence of oxygen, releasing methane, carbon dioxide and traces of hydrogen sulphide and moisture in the process.

This methane is largely identical to the mains gas we use to cook with and heat our homes. It is also given off from landfill sites when food waste is dumped there. Currently, around 50% of UK landfill sites capture and clean up this gas for fuel use however, the rest don’t, allowing it to escape into the atmosphere.

Methane is a greenhouse gas 20-30 times more potent than CO2. Reducing methane emissions is a an effective way to combat climate change. Scotland has taken the bold move of banning food waste to landfill from 2014, while Wales has committed to zero waste by 2050. England remains on the fence and currently relies on raising landfill tax to dissuade people from dumping waste there.

Leaves

We applied for full planning permission for our pilot 2m3 AD system after having found a home at Camley Street Natural Park – a London Wildlife Trust environmental education centre set in a beautiful 2-acre nature reserve by the canal near Kings Cross.

While waiting for consent to build, we were commissioned to produce a report for the Technology Strategy Board’s Future Cities Competition, where cities were encouraged to dream up ways of integrating systems within a dense urban area to demonstrate sustainability, efficiency and better quality of life.

Our proposal naturally focused on micro AD and how networks of small-scale digesters ranging between 1-500m3 could help reduce waste transport and emissions, save waste management costs, generate local energy and employment and produce fertiliser to support local food growing and greening projects. The report quantified these outcomes and explored the business case for their sustainable development post funding.

Meanwhile, with planning permission granted, we began building the infrastructure for our pilot plant at Camley Street, a process that would take us through the cold winter of 2012. It was freezing! A welcome interruption in the spring of 2013 came with another feasibility study, this time for WRAP – Waste & Resources Action Programme – a government funded body focused on waste prevention and recycling.

While the Future Cities report had a theoretical budget of £24 million to play with (which eventually went to Glasgow), WRAP’s DIAD II fund was more modest and realistic, focusing specifically on driving innovation in the AD sector. We scaled down our initial AD network concept to three sites within a 1-mile radius. A potential fourth self-funded site was 6 miles away.

WRAP liked the proposal. They felt it was both innovative and achievable and granted us funding to demonstrate the network.

For a group of engineers, academics and community bods, this was hugely exciting! A chance to show how decentralized, closed-loop, integrated thinking can create sustainability and benefits on multiple levels. Aside from environmental and economic gains, the project has great potential to develop educational and community engagement opportunities as the technology is easier to grasp at a more human scale. People get to see the benefits close up and can be inspired by it.

Site 1 Camley Street Natural Park would be upgraded to include a micro CHP (combined and power) unit. Its about the size of a boiler and generates electricity and heat from the biogas, which will be scrubbed (cleaned) to remove most of the hydrogen sulphide, moisture and CO2, leaving largely methane. The design is simple and if it works as well as we hope, will be a massive cost reduction on the nearest scrubbing unit we can find. The site will also host algae cultivation and low cost hydroponics to utilise fertiliser and CO2 from the AD process. We plan to grow Spirulina and Chlorella, two stains of algae with regenerative properties used in cosmetics and soap making, and as a food supplement.

Site 2 The Calthorpe Project on Grays Inn Road is a well-established community garden and centre. The biogas there will be used raw to heat polytunnels and a greenhouse - a fantastic use as the CO2 and sulphur released during burning helps plant growth, so nothing is wasted. The fertilizer will of course be extensively used on-site. The Calthorpe’s 1m3 modular digester will be a low-cost, manually operated system that will become affordable to community groups.

Site 3 Alara Wholefoods was established in 1975 with a factory and successful wholefood shop, both close to Kings Cross. Their commitment to becoming the most sustainable business ever, led them to manufacture high quality organic wholefoods. They have also created a 300m2 forest garden, vineyard and orchard on their factory grounds - ample space to utilise the fertiliser from a 6m3 digester. The biogas there will be scrubbed and compressed to biomethane for use in their local food delivery van.

Site 4 Loop Management Services based in Waltham Forest collect a wide range of recyclable waste including half a tonne of food waste daily. They are keen to keep on improving their sustainability both economically and environmentally. We proposed a 20m3 system with the ability to convert biogas to biomethane for their collection vehicles. We’re still waiting to see if this might materialise but it is worth mentioning as the economics of this size work out nicely with a 5-6 year payback period.

This may still seem a lot in today’s world but is worth it for a technology that saves waste miles and makes use of what might otherwise be a wasted resource, not to mention the benefits of recycling nutrients and closing the urban waste-energy-food loop. As the technology is more widely taken up, these costs will reduce. This is what we are working towards.

Early flowering

We launched the pilot system at Camley Street Natural Park on October 4th this year. Commissioning is still in progress, which means some feedstock has been introduced into the digester from established digesters as a starter culture complete with microorganisms. The heating has just been turned on as the organisms like to be around 38-42oC. Energy wise, this along with power used for mixing and monitoring is considered a parasitic load and must be carefully managed to ensure systems produce a positive net energy total.

We use a cargo bike for collections and have so far collected 200kgs food waste from local businesses including Kier, a large construction company championing our cause and supporting us with timber, St Athans Hotel, whose manager Stefan Geyer is Chair of the Permaculture Association, and London Contemporary Dance School, whose CEO, Kenneth Tharp OBE personally made sure they were involved with the project at the early stage.

The more businesses we talk to the more we are realising the scale of available food waste and how many people there are wanting to do something useful with it. One 2009 statistic described the volume in Central London as 200 tonnes produced in a 2-mile radius daily!

Future fruit

We are currently in early discussions with R-Urban a Hackney Wick-based initiative and Cob in the Community, both with exciting visions involving urban micro digesters in closed loop demonstrations.

Cob in the Community’s proposal is evolving around a 20m3 digester insulated with cob and straw that would become a beautiful, educational sculptural feature. Site expansion would include a café and resulting food waste complete with Loowatt waterless toilets providing AD ready feedstock.

R-Urban Wick aims to set up a citizen-led Re-Use Centre in Hackney Wick & Fish Island (HWFI), a public facility supporting and making public the culture of re-use, invention and resourcefulness that is embedded in the area. Their proposed centre would include a 20m3 digester, workshops, tool library, kitchen, shop, archive, research space / artist residency space.

For both proposals, community engagement opportunities would be maximised throughout the building and operational phases and the AD systems could be modular, able to expand if more food waste became available.

LEAP’s previous research contributes a number of additions; pre-processing biomethane collection vehicles operating locally with parallel zero carbon cargo bikes collections to canalside drop points; biomethane barges to transport this waste plus residential barge food waste and sewage pump outs collected en route to the digester; barges could also distribute fertiliser to users along the canal.

By utilising AD byproducts methane generated heat and electricity, CO2, sulphur and fertiliser, a range of micro enterprises could complete the closed loop demonstration;

  • polytunnels with raised beds for food growing,
  • micro algae cultivation to produce ingredients for soap and cosmetics making,
  • hydroponics
  • aquaponics (micro fish farming) and
  • a micro brewery (thermal synergy with AD).

Waste products from these activities would be fed back to the digester.

These projects would benefit temporary sites or brownfield sites by the canal, which could be regenerated using digestate and provide a training ground for young unemployed people learning to grow food. Any potential site owners out there…?

Part of the groundswell

The future is a creative act we all participate in on a day-to-day basis. We tap into rich seams of energy and inspiration when we focus on the best we can be, the best we have to offer at any given time. In this collective endeavor, every contribution counts, be it local or global, corporate or community individual or state. We hope these micro ADventures can contribute to the emerging vision of sustainability and joined up thinking that may just carry us through the 21st century.

To find out more about the LEAP project or visit the pilot system:
www.communitybydesign.co.uk

To speak to Andreas about the R-Urban Wick Re-use Centre proposal contact:
www.r-urban-wick.net/contact

To speak to Linda about the closed-loop, sculptural, cob-insulated digester proposal:
www.cobinthecommunity.org
www.transitionfinsburypark.org.uk/Cob