Biofuel from waste is a promise still to be fulfilled. However, a pioneering project, led by British Airways (BA), which is due to begin at the end of 2015, could go some way to achieving this goal. If the ‘Greensky’ project goes ahead as planned, Europe’s first waste-to-biojet fuel plant will be based on the former Coryton oil refinery site at Thurrock in the Thames Gateway, east London, UK.
The plant will be fed by organic municipal solid waste (MSW), such as paper and food waste, from households. In contrast, most biofuels on the market today are based on woody biomass or energy and food crops. From 2017, the Thurrock plant is expected convert around 575,000t each year of waste normally destined for landfill or incineration into 120,000t of liquid fuels (bio-kerosene). BA has committed to buying 50,000t/year of the jet fuel, enough to power its flights from London City Airport to all over Europe and New York, US, twice over, with carbon savings equivalent to 150,000 cars.
The project will use high temperature plasma gasification technology, developed by fuel supplier Solena, to transform the waste into synthetic gas, or syngas. This syngas will be cleaned and passed through a Fischer–Tropsch system, designed by technology company Velocys, to produce the jet fuel.t The plant will be capable of processing 20–50% more waste than conventional gasification technologies. According to Leigh Hudson, environmental manager at BA: ‘We saw plants in Johannesburg and Qatar transforming solid carbon into liquid. That gave us the confidence early on that our technology would be able to use the fuel.’
But despite the fact that Solena has acquired certification for its fuel, the project still faces several challenges. Construction has already been delayed. Independent observations from the UK Green Investment Bank and others indicate the plant still requires another £400-500m in funding, an estimate that has risen from £200m in 2012. Contracts need to be agreed with waste providers.
The site has been acquired and agreed by the parties involved, but still requires planning and other consent for the plant. ‘We lack an environmental permit and are engaging in dialogue with the Environment Agency,’ explains Hudson.
The economics of the operation are also under question, including for example, the financial principle behind the waste collection. UK organisations disposing of waste through landfill currently incur typical gate fees of £88–129/t, though there are incentives to divert it to alternative treatments. For example, sending food waste to anaerobic digestion would cost £25 –66/t.
In theory, this is good news, but the alternative gate fee is not high enough. ‘Solena needs most of the tipping fee as its revenue stream. Incineration plants competing on contracts can outbid the company,’ points out Clare Curry, biofuels analyst at consultancy Bloomberg New Energy Finance. If the fee is raised too much, the landfill deterrent effect will not work. As a consequence, other incentives and subsidies would be helpful.
One potential incentive is the Renewables Obligation Certificate (ROC), which provides government financial support to innovative energy technologies. ‘Some energy-from-waste plants are eligible for these [grants]’, explains Curry. For example, electricity produced from advanced gasification and pyrolysis can attract two ROCs per megawatt hour. However, the government has not stated that the Thurrock biofuels plant would be eligible. ‘It would help the gasifier if Solena were to get ROCs, but bio-kerosene doesn’t come into the ROC agreements,’ says Curry.
Inclusion in the UK Renewable Transport Fuels Obligation (RTFO) might also go some way to addressing the problem. This requires particular road fuel suppliers to integrate a small proportion of biofuel into their products, but does not include airlines. However, many of the airlines in the UK have opposed this. ‘They want the carrot without the stick. The question is whether opposing a biofuels mandate means they shouldn’t receive the subsidies,’ comments Curry.
While such opposition may cast doubts on their motivation, it is perhaps not surprising that some BA managers might view such a first-of-a-kind plant with caution. The opportunity to exploit the waste is there, however. According to the Green Investment Bank, the annual proportion of untreated and post-recycled waste used in energy-from-waste facilities such as incinerators will rise from 20% in 2012 to 56%, which equates to around 25m t in 2020. The Thurrock plant requires only 0.5m t/year.
Greener US flights
Meanwhile, the outlook for using MSW as a biofuel looks more promising for a similar plant in the US. Also reliant on Fischer–Tropsch technology, the plant is based in Nevada and is managed by energy start-up Fulcrum Bioenergy. The company, which is ahead of Solena and BA, ran a demonstration plant processing 5t waste/day over four months in 2014. Following this successful trial, and with the relevant environmental and planning permits awarded, construction has now begun on a plant capable of processing 100 times as much waste. This plant is due to begin production in 2017 and is expected to supply fuel at the same price as bio-kerosene.
The Asian airline Cathay Pacific has staked an equity investment in Fulcrum and made an initial commitment to buy 375m US gallons of the biofuel for 10 years – around 2% of the airline’s current fuel consumption.
Fulcrum chief executive, Jim Macias comments that assumptions about previous hydrocarbon-to-liquids plants may not be valid for waste-to-liquids. The risks are different. For example, the quality of the waste input is usually less homogeneous than many other types of feedstock used in similar technology. ‘It can be a problem. You could have a heavy wet dense mass followed by fluffy, light, shredded paper pellets. It has to be mixed so there is not that much variability. After that, it becomes a pretty smooth organic mix so we have a continuous flow,’ he explains.
Lukas Rohleder of Aireg, a German organisation promoting sustainable aviation fuels, agrees, ‘The challenge with MSW is the pre-Fischer–Tropsch stage. With household collections, everything is constantly changing. Pre-treatment of waste is an issue. It can be dealt with but it is a practical problem.’
Moreover, as Macias points out: ‘The gasification process needs to be robust enough to handle the variances. It needs to be reliable and to be able to process at scale so you get a high enough carbon conversion.’ Fulcrum tests show the company has achieved a 90% carbon conversion, which is considered high. ‘This has a big impact on economics,’ he says
Scaling up the plant raises other potential challenges. ‘The chemical reactions in the process are different when the gasifier is bigger and the process takes place at a larger scale. For instance, there may be other byproducts.The carbon conversion may not be as efficient. The plant will still work, but the question is how well,’ he says.
Careful integration of the different steps in the process will be needed to ensure maximise efficiency. According to Curry, any company scaling up a plant of this kind is likely to run into problems: ‘The facilities can be so temperamental. It can take a couple of years to get them up and running. A lot of the challenge is in the gasifier.’
Given the fluctuating price of oil, the fuel price parity with kerosene could be a risk factor. But Macias claims the company has this under control. ‘We have a long-term waste contractor who is supplying trash at a fixed cost so there will be no variances is input costs,’ he says, indicating that this will help manage pricing volatility at the other end of the process.
Equally promising is a Scandinavian process that uses waste animal fats and vegetable oils. NEXBTL diesel is a fuel manufactured by Finnish company Neste Oil and produced in a patented vegetable oil refining process. Plant oils undergo a chemical reaction, converting them into paraffins. The final product is chemically identical to conventional diesel and requires no modification.
The NEXBTL fuel comprises hydroprocessed esters and fatty acids (HEFA) and has properties similar to the biomass-to-liquid diesel fuels produced by the Fischer–Tropsch synthesis. NEXBTL has also received its fuel certification and meets EU standards. In 2014, US aeroplane manufacturer Boeing successfully tested the biodiesel fuel as a component of its aviation fuel in the 787 Dreamliner.
‘This is an option we really like,’ states Rohleder, crediting Neste Oil for its versatility and perseverance through trial and error. ‘They followed a multi-feedstock strategy – the more flexible the refinery, the better. Neste started out with palm oil and as a result of sustainability concerns, 60% of the feedstock is now waste like animal fats and fish oil. By 2017 they will only be using waste,’ he says.
Future green flights
Rohleder’s remarks draw attention to the long-term nature of aviation biofuels development as experts search for the best and most efficient technology. Waste products are a sustainable alternative to food and even energy crops. Woody substances have also been tested as waste biofuel feedstocks, but they have their own problems.
‘Woody biomass is a technically better feedstock but is expensive,’ comments Curry. Breaking down the ligneous substances may require more difficult or complex processing. Risks incurred by the technology developers are high. One notable victim is Choren, a company that went bankrupt in 2011 while constructing a wood-based biomass-to-liquids plant in Freiberg, Germany. The following year, a US wood-based biofuels company Rentech closed its Colorado demonstration plant, which converted cellulosic biomass into synthetic gas.
Of the more recent developments, Cathay Pacific’s willingness to take a share in Fulcrum’s venture is among the most positive. More generally, airline financial engagement in biofuels has been noticeable for its absence in terms of capital investment or financial partnerships. The industry’s defensiveness against environmentally-friendly policies has been widespread. Typically, arguments concern international competitiveness and level playing fields.
‘If they were serious, they would always be willing to take the financial risk to do this stuff,’ comments Jeff Gazzard, a green campaigner at the NGO Aviation Environment Federation (AEF). His scepticism may be well-judged. In a road map published in 2014, the industry coalition Sustainable Aviation predicted biomass-to-liquid fuels will be commercially available by 2020.
Future generation biofuels, such as pyrolysis and sugar-based fuels, are expected to be developed in the next decade. By 2020, an optimistic scenario by Sustainable Aviation predicts a potential global supply of sustainable fuels for aviation at 1.3mt. By 2030, 13m t of sustainable fuels may be produced globally, equivalent to 0.7–3.3% of global aviation fuel use.
The volumes are an insignificant fraction of the amounts needed to cut fossil fuel use and carbon emissions.
However, they will provide the airline industry with public support for business as usual. Technically, aviation biofuels are feasible but the small scale envisaged reflects a missed opportunity.
Elisabeth Jeffries is a science writer based in London, UK