Growth industry

Small refineries could convert locally-grown biomass into fuel, power, heat and chemicals for neighbourhoods across the UK – a move that could help the government to secure energy supplies and reduce carbon emissions. It could also revive the country’s flagging agricultural sector.

The multi-tasking refineries are being researched by a consortium of universities with backing from Intensified Technologies Incorporated (ITI), a spin-off from academic research which supplies renewable energy solutions to electricity generators around the world.

While many in the energy industry have exploited the conventional wisdom of economies of scale to grow to their current stature, the biorefinery researchers believe instead that small can be beautiful, if it is well designed.

They want to perfect relatively small plants that take biomass produced in the neighbourhood and turn it into fuel, energy and chemicals required by the same area. To achieve this miniature marvel, the consortium is trying to squeeze more from less by integrating and intensifying several processes.

‘Biomass can be converted to high-value chemicals,’ explained Prof Galip Akay of NewcastleUniversity. ‘The remaining residual biomass can then be converted into bioethanol through fermentation. And the residue from that process can be gasified to obtain syngas.’

The trick that his team is trying to pull off is to integrate all these processes and squeeze them, so that they become viable within one small unit, extracting the maximum from the biomass feedstock in the most efficient way.

Intensive gasification is already a developed procedure, supplying fuel for a 1MW electricity generator in Scotland, and two more are under construction. Akay’s team will continue to improve gasification and the other processes for the biomass refineries are being scrutinised. Several of them will make use of materials which are riddled with micropores and nanopores.

‘These are polymers, metals and ceramics,’ said Akay. ‘The porous polymers were originally developed at Unilever Research some 20 years ago, but we have better ones, made in minutes rather than days by using microwaves.’

The team aims to use the porous material to grow enhanced bacteria. ‘Depending on the size of the pores in the polymer we can control the physiological stress of the bacteria and then it will behave differently,’ said Akay. ‘The productivity of the bacteria can increase 20 or 30 times.’ One strain will speed up the growth of the biomass so that the refinery will have a ready and predictable supply of feedstock. It will allow the biomass to be grown on marginal land and in drought areas, claims Akay.

Another bacteria will be enhanced so that it is can ferment the biomass faster and more thoroughly than conventional bacteria, boosting the efficiency and throughput of the plant.

Metals with continuous pores decreasing from 100 microns to less than 10 microns in diameter will be used as catalysts in the biorefinery to intensify the extraction of chemicals from the feedstock. ‘All of the channels are interconnected so the active sides of the catalyst are available at all times,’ said Akay. ‘It has a lung-type structure, so the accessibility of the catalyst is never compromised.’ Ceramics with micropores have recently been developed and may find applications for intensifying some of the processes in the biorefinery.

The feedstock for the refinery may also come from sources other than agriculture. Biomass waste such as municipal solid waste, sewage sludge or agricultural residues may be converted directly to bioethanol via gasification to produce syngas, which must be cleaned and its composition controlled.

‘Its gases should be separated into components hydrogen, carbon monoxide, methane and carbon dioxide so they could be used as chemical building blocks of larger molecules such as ammonia, ethanol and methanol,’ said Akay.

Alternatively, syngas can be used as a fuel for combustion engine or fuel cells to generate electricity. These operations should be carried out at high temperatures to enhance efficiency.

Syngas-to-power/higher chemicals conversions also require catalytic reactions. However, it is essentially a ‘dirty’ fuel and must be cleaned of tars, toxic components and particulate matter. The team aims to do this by developing high- temperature catalysts of metal that function at up to 1,600oC.

Following the publication of the government’s energy review, it looks like biorefineries would fit well into future strategies. They will also help struggling farmers. ‘Only 200 years ago the world depended on biomass for heat, light and food,’ said Akay. ‘We believe it will be a real alternative through process integration and intensification.’