Cream of the crop

Barfoots of Botley has created a big green monster with a voracious appetite. But there's no need to run screaming for the hills. Far from terrorising the local community, this particular beast is entirely benign. The anaerobic digestion (AD) facility on Barfoots' site at Sefter Farm, West Sussex breaks down vegetable waste to produce biogas which fuels two containerised combined heat and power (CHP) units. Although it is a gentle giant, managing director Julian Marks says the AD facility presents all sorts of microbiological challenges: "An AD plant is a living creature. Getting it into a steady running state is part art and part science. The key to success is the quality of our site managers [three people are employed full-time on the AD facility] and their ability to focus on what's going on inside the tanks." For Marks, it's like investing in a 1,000-cow dairy herd: "These projects are not the same as other renewable schemes like wind turbines or solar farms, which have relatively low maintenance demands. "Rather, we have begun a 25-year relationship with a creature that needs to be fed and watered, kept happy in a dietary sense and well maintained." Barfoots' CHP/AD project was initiated in 2007, chiefly to help it dispose of its green waste in an environmentally friendly way. The company processes around 100,000 tonnes of vegetables annually at its Sefter Farm factory. This results in 20,000 to 25,000 tonnes of waste (enough to fill more than a thousand lorries). The energy element is two CHP units Marks explains: "We looked at various options for dealing with our vegetable waste including composting, animal feed and landfill, but after a lot of research, including visits to Germany and Austria (where anaerobic digestion and CHP are already well established technologies), we settled on an AD project, the energy element of which is the two CHP units." Heat generated by these units is used to keep the digestion plant at 40 deg C and for pasteurisation of the bi-product from anaerobic digestion – an organic fertiliser used to feed the company's crops. Construction of the AD plant began in 2009 and took 12 months to complete. Barfoots itself was the main contractor; it appointed a project manager to manage the sub-contractors (civil engineers, building construction contractors and personnel from German AD technology provider MT-Energie) who actually built the facility. The CHP/AD system cost around £5 million to build and Marks estimates the payback to be around seven to eight years. Barfoots funded the project from three sources. It received a grant from the now defunct South East England Development Agency (worth around 15% of the project cost). It also employed lease funding from asset finance provider Lombard (25%) and its own resources (60%). The company had no direct finance from the banks. The plant, which was officially opened by Sainsburys boss Justin King in mid-2010, makes Barfoots more than self-sufficient in energy; not only does it produce enough electricity to power its entire site, but it is also a net exporter of power to the National Grid. Depending on the time of the year, Barfoots exports up to 70% of the electricity it generates. The company earns Renewable Obligation Certificates (ROCs) for every MwH of electricity its CHP?units generate. ROCs are traded instruments, the value of which goes up and down depending on the demand from the energy generators for clean energy. Sustainability credentials enhanced As well as offering powerful financial advantages, the AD and CHP system has, says Marks, enhanced his company's sustainability credentials, significantly reduced its reliance on artificial fertiliser and improved its agronomic performance. It has also enabled Barfoots to create a new and diversified revenue stream. Barfoot Energy Projects was established in 2009 to develop renewable energy projects, providing services to farmers and landowners wanting to develop AD and other renewable energy projects. But, perhaps most significantly, CHP has given Barfoots energy security, as Marks explains: "We are no longer reliant on the market for our energy. We have agreed our own cross charge for the energy we use and that gives us certainty in terms of energy price and supply." This has freed Barfoots to make relatively small, but environmentally sensible changes to its manufacturing operation such as replacing most of its diesel forklift trucks with larger electrical forklifts which it can charge with its own electricity supply. The company's engineering van, which is used to connect its two local sites, is also now electric and it has just introduced the first electric car into its pool car fleet with more to follow. Barfoots has clearly enjoyed a host of benefits from installing its CHP/AD plant, but only because it went about selecting, installing and commissioning the equipment properly. Best practice dictates that, even before considering CHP, you should investigate simple energy efficiency measures such as better insulation, low energy lighting and boiler optimiser controls. This should allow you to select a smaller CHP unit for your site. Ideally, use the same company to drive down energy consumption on site and supply the CHP system. CHP only delivers savings when it is running at its optimum level and it will need to be serviced regularly to ensure this happens. So, engage a reputable supplier with a track record and a strong maintenance arm (see the Combined Heat & Power Association website (www.chpa.co.uk for a list). Make available to the CHP supplier all the energy data you have collected from your manufacturing site, ideally half hourly electric and gas as well as the specific thermal loads. There are essentially two ways to pay for a CHP system: - Capital purchase (or 'on balance sheet' financing), which can be financed by internal funding, debt finance or leasing. - Operating lease (or 'off balance sheet' financing) which can be financed by an equipment supplier, energy services company or private finance initiative. The Carbon Trust – an independent expert on carbon reduction and sustainability – has published a useful booklet explaining these options in more detail and how to select the right one for you (www.carbontrust.com). Five plugs for CHP 1 Combined heat and power (CHP) is the simultaneous generation of usable heat and power (usually electricity) in a single process. The electricity is generated on or close to your site, allowing you to capture and use the resulting waste heat for site applications. 2 In the UK, three industrial sectors account for around three-quarters of CHP electrical capacity, according to the Carbon Trust – chemicals (33%), oil refineries (32%), and paper and publishing and printing (10%). 3 Sites that benefit most from CHP are typically intensive energy users operating a 24/7, shift-based pattern. CHP is only viable if you have a high and constant demand for heat, typically at least 4,500 hours per year. However, it could be suitable on some sites with a lower heat demand, particularly those with a high demand for cooling. 4 Sites can see annual savings of up to 20%. 5Properly sized and installed CHP qualifies for 'Good Quality' status under the government's Combined Heat and Power Quality Assurance Scheme (http://chpqa.decc.gov.uk). This offers an exemption from the Climate Change Levy, enhanced capital allowances and reduced business rates.