Shropshire Council is proposing to convert the former biodigester site on Coder Road to produce biochar, a carbon-rich organic solid partially combusted in a low-oxygen environment. Agricultural and forestry waste will be carbonised under temperatures of up to 700°C in a process called ‘pyrolysis’. The process releases gases, and sometimes bio-oils, and leaves biochar, a solid residue of at least 80% elemental carbon.
The council intends to submit a planning application this month. A drop in session to explain the scheme and answer questions is to be held on Wednesday, from 2pm to 7.30pm at Ludlow Library. Council leader Lezley Picton will also be at the library from 2pm to 5.30pm to answer questions about Shropshire Council.
Biochar is useful in agriculture. It slows water runoff from fields, improving water retention and helping reduce flooding. It helps the soil retain nutrients. It can also increase microorganisms in the soil and be used for remediation of contaminated soils. Crop yields can be increased by up to 10%.
Agricultural use of biochar is not new. Terra Preta de Índio, also known as the “Indian black earth” has been used by indigenous people in the western Amazon for centuries, if not longer. The proposed Ludlow biochar plant will use forest and agricultural vegetation. It will not use food waste or manure.
Carbon sequestration is seen as a significant tool in slowing global warming. Biochar has a higher carbon content than most biomass and is slower to decay. That makes it useful for storing carbon, a use recommended by the International Panel on Climate Change (IPCC). Biochar is a low cost, small-scale addition to the efforts to remove carbon from the atmosphere. However, some researchers suggest the capacity of biochar to sequestrate carbon might be overestimated.
Biochar could also reduce use of synthetic fertilisers, which are high emitters of carbon, both during production and use on fields. Biochar remains in the soil and does not need be applied annually like conventional fertilisers. Reduction in the use of synthetic ammonium nitrate fertilizers will be beneficial as almost all is imported. It is also due to attract a carbon tax while biochar allows businesses to gain carbon credits.
Shropshire Council has not revealed the specific cost for Coder Road but last September it set aside £2 million of unused capital allocation (borrowed money) for a Shropshire biochar demonstration plant in Shropshire. Such a plant would produce a minimum of 500 tonnes biochar a year. It is anticipated that the £2 million investment will be paid off within six years. It council estimates that a plant will cost £226,000 a year to operate, with £621,000 income from sales of biochar and carbon credits, along with charges for receiving biowaste. It is assumed that the biochar will sell at least £400 a tonne.
According to Shropshire Council, the local impacts of the biochar plant will be small. The former biodigester site is on an industrial estate adjacent to the A49 bypass. Noise is estimated at up to 53 decibels, not untypical in a home environment, for example a washing machine. This is unlikely to be heard by residential properties, the nearest of which is 200m away, against the drone of the A49. The council is says there will only be two to four small lorry movements a day. It is estimated that the plant will use 5,000 to 6,000 tonnes of feedstock a year. The council asserts there will be no smells and smells are unlikely given the nature of the feedstock and the closed vessel pyrolitic process.
Emissions will be scrubbed in a flue before discharge: 99% of sulphur and chlorine will be removed, along with 95% of nitric oxide and nitrogen dioxide will be removed. No methane will be admitted. Presumably the methane will be used to generate electricity to power the plant and any excess fed to the grid.
There are many questions to be asked about this proposal. For example, the type of feedstock affects the quality and use of the biochar. How will this be controlled and will it be maximised for agricultural benefit? Is biochar suitable for the all the varying soils of Shropshire? Is wood the right feed stock for the best biochar? The pyrolysis process generates methane. How will this be converted into energy?
Although, I am supportive of this technology and its location in Ludlow, I will be not making any comments on the specific application until it comes to the Southern Planning Committee next year.
If you want to find out more, visit the drop-in event Wednesday 6 November, from 2pm to 7.30pm at Ludlow Library.