Bioconversion gains traction

Envirotec looks at recent developments with biorefining and converting biomass into useful chemicals or renewable fuels.

UPM Concept Car inside
The Biofore Concept Car showcases the potential of bio-materials in car design.

Technology sometimes has a recognisable provenance in science fiction or visionary inventions of the distant past, though hindsight tends to bring amusement at the assumptions underpinning the original idea. The reliance of Leonardo da Vinci’s ornithopter on flapping a set of artificial wings sufficiently quickly to enable flight now seems endearingly wrong-headed.

The notion that material from your trash could simply be converted into fuel for your car is recognisable in the kitchen-like appliance protruding from the rear of the Doc’s car in the opening scenes of Back to the Future part 2.

While the fictional timeline of the film – 2015 – has come and gone, inviting perhaps underwhelming comparisons with the technologies of today (no flying cars), the possibility of converting household trash into a sustainable fuel seems to be hovering into view. One seemingly significant area of recent progress draws not on the promise of nuclear fusion (pace the Doc’s “Mr Fusion” contraption) but on one of the oldest biological processes on Earth.

A collaboration between Sekisui Chemical Co and Italian biotech firm Lanzatech announced in December that it had demonstrated the possibility of converting unsorted municipal solid waste (MSW) – normaly destined for incineration or landfill – into useful materials that would normally come from fossil fuels or sugars. While a laboratory-scale demonstration dates back to 2013, Lanzatech says the technology “has now been demonstrated at pilot scale, achieving commercial productivity and stability targets.”

The system combines an existing gasification system at a landfill site with a novel fermentation approach developed by Lanzatech, where microbes grow on gases (rather than sugars, as in traditional fermentation). The microbes in question belong to a family called acetogens, with ancient origins dating to the hydrothermal vents of underwater volcanoes at the dawn of life on Earth. In this context the process produced ethanol.

Where a similar gas mix of CO, H2, CO2, H2S and CH4 is present, the same mechanism can seemingly be exploited for industrial purposes, as Lanzatech does.

At the core of the firm’s technology is a process that uses proprietary acetogens. The approach gives rise to various products, some of which are immediately usable as fuels or chemicals, while others can be converted into common chemicals, or fuels to replace some of those normally derived from fossil sources.

Elsewhere on the gasification front, what looks likely to be the first plant in the US to produce biofuel from MSW using gasification is currently under construction in Nevada. Infrastructure, energy and waste company Abengoa received Notice to Proceed for the project in November, at which point the firm expected the engineering, procurement and construction works to take over two years. The plant will have the capacity to produce 10 million gallons of biofuels per year, to be used in the aviation sector.

Progress with lignin?

A traditional challenge in the effort to convert biomass to something useful – rather than just burning it – is lignin, the material responsible for many of the structural properties of trees and plants. The large quantities of this material produced by facilities like paper mills are simply treated as waste at present, but it has great potential as a replacement for many of the useful materials currently sourced from the oil industry.

Lignin was seemingly a talking point in December at EcoPro, one of the largest environmental exhibitions in Japan. At the event, UPM showcased a range of useful products made from lignin-based residues – not only fuel but materials.

A futuristic car concept was unveiled – the Biofore Concept Car (see photo, above) – seemingly aimed at highlighting the existing potential to build many car components and sub-systems with bio-materials rather than plastic. For example, door panels, dashboard and side skirts were made from one of the firm’s biocomposite materials made from cellulose fibre and plastics, while a thermoformable bio-material was used in the passenger compartment floor and door panels. The car also runs on a wood-based renewable diesel, UPM BioVerno, which the firm says has been produced 100% outside the food value chain.

In December The Energy Research Center of the Netherlands announced it had developed a novel process to fractionate biomass such as hardwood chips and wheat straw, providing, so it seems, a high yield of “valuable building blocks for biobased products” at potentially lower cost and process energy demand than alternatives. The research has been published in the journal Green Chemistry. The group used feedstocks of wheat straw, corn stover and various hardwoods such as poplar, beech and birch.

According to the group: “The isolated lignin showed remarkable characteristics as compared to lignin obtained by other pretreatment processes,” with promise as feedstock for the production of aromatic polymers and monomers. Future developments are promised via  cooperation with the Fraunhofer-Center for Chemical-Biotechnological Processes, which so far has resulted in the first successful scale-up tests in “the lignocellulose biorefinery pilot plant.”

While a shift towards renewable fuels for transport seemed well underway in the late 2000s, progress since then has slowed, giving way to an ascendancy of electric, hydrogen and hybrid vehicles. The UK’s government’s enthusiasm seems to have waned. Since 2012, road fuel in the UK has been blended with approximately 4.75 percent bioethanol. The UK Department for Transport (DfT) has stalled on lifting the blend level further, despite making initial recommendations along those lines.

The Financial Times recently reported on the uncertain fate of the UK’s two biggest bioethanol plants, Vivergo in Hull, and Ensus in Teeside. Both facilities use feedstocks sourced from agriculture.

The Ensus plant, which has cost £350 million so far, has been closed for around half of its three years of operation. It was sold in 2013 to the German-owned CropEnergies, who promised further investment prior to announcing a shutdown in February 2015, blaming the drop in oil prices, low bioethanol prices, and a “drawn out political process” in the EU around increasing the use of renewable fuels in the transport sector.

Environmental groups have also questioned the wisdom of using crop feedstocks for fuel production. A statement from the Department of Transport in 2016 suggested a shift in government priorities from crop-based biofuels to those generated from waste, as a better way of meeting EU targets.

A number of interesting waste-to-biofuel projects seem to be in the pipeline, with gasification and biorefining appearing to be the most promising technologies.