Small Scale Food Waste to Biogas AD Systems Ready to Deploy in UK

Burdens Environmental has completed trials of a demonstrator facility in South West Wales, which is now accepting waste from Carmarthenshire Council and HRH Prince Charles' estate in Wales

20 July 2012

Bristol, UK based small scale anaerobic digestion systems supplier, Burdens Environmental has completed trials of a demonstrator facility in South West Wales, which is now accepting waste from Carmarthenshire Council and HRH Prince Charles' estate in Wales

The company claimed that the facility is the UK's first commercial small scale anaerobic digestion (AD) system for localised food waste treatment, and that it now plans to roll out it compact food waste treatment plant.

According to Burdens the system has been designed to speed up the adoption of AD food waste treatment plants in the UK by making them commercially viable and thereby increasing recycling rates for municipal and commercial food waste across the country.

The company added that currently a very small percentage of all food waste in the UK is recycled through anaerobic digestion, instead going to landfill, composting or incineration.

The issue, according to Burdens is that there are only three dedicated AD food waste treatment plants in the UK recycling municipal sourced food waste out of a total of 32, including its own pilot site at Llangadog in Carmarthenshire, which will become the company's first treatment site for domestic waste. 

The other facilities are said to treat different types of food wastes from catering outlets, food retailers and manufacturers and are significantly larger, performing a central waste treatment function rather than a local service.

Target market

The company said that its new compact process is being targeted at private waste collection companies, in house waste management operations of local councils and those companies in the food chain, such as retailers, food manufacturers and catering providers.

Each Burdens system will be capable of handling between 3000 and 5000 tonnes of food waste per year, and the company said that it is offering a fully funded solution for the modular waste treatment plants, as well as an option to buy outright.

The fully funded package will involve the company paying its customers to run the operations, with a full maintenance programme and rent for the land on which it will be located being covered by Burdens.

In return, the company said that it will benefit from the Feed in Tariff and Renewable Heat Incentive linked to the renewable energy outputs of the recycling process.

In addition, full turnkey plants will be available for between £850,000 and £2 million, which the company said would provide a rapid payback through significant operational savings, as well as revenues from energy generation and gate fees.

The company added that its system is the first digester of its size to be Animal By Products Regulations (ABPR) compliant, which means that it can recycle general food waste, including meat.

It also claimed that the system meets compost, soil and land use regulations (PAS 100, PAS110). The biofertiliser generated is used as a beneficial fertiliser on local farm land.

The process

Burdens said that its patented digestion process involves all food waste passing through a macerator and chopper pump before feeding into holding tanks.

Following a three day hydrolysis and pasteurisation period, the contents of the tanks are emptied. At this stage the high fibre content is screened off and the remaining liquid or 'soup' is pumped into the main digester.

Biogas production takes place in the main digester, which the company said is constantly being replenished by the input of new food waste.

Liquid from this tank is recirculated to wet down the arriving food waste, with the surplus expended liquid used as a beneficial biofertiliser. Burdens said that the recirculation of liquid within the process ensures very high levels of heat efficiency minimising heat demand from the process. 

In a process designed specifically for this type of system, the company said that the separated high fibre material (mainly lignin) is combined with waste wood to produce a high quality low ash pellet for wood burners. 

The biogas produced in the digester is stored ready for use within the site generator, which can supply electricity and heat to be used as required.

Research and trials

According to the company extensive trials of the AD plant have been carried out over a two year period at a demonstrator in Llangadog.

In addition, Burdens said that it has established a track record in the design and delivery of small scale digesters in the prison service with the latest plant at HMP Oakwood currently being commissioned.

This has proven that the separated hydrolysis technology works very efficiently at a smaller scale and is capable of generating between 20kWe-150kWe electricity per annum in addition to heat and up to some 100 tonnes of solid biofertiliser, the company said.

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