Sustainable biofuels

C&I Issue 12, 2009

Second generation biofuels plants – due to start coming onstream from next year – promise to be greener and more sustainable than their predecessors. They will take cellulosic biomass, often produced as wastes, and transform it to transportation fuels with the emission of 80-90% less greenhouse gases compared with gasoline. Current first generation plants emit anything from 0 to 90% fewer greenhouse gases, depending on which feedstock is used. Plus, rightly or wrongly, they also stand accused of pushing up food prices by relying for their feedstock on conventional food crops.

‘The challenge of sustainable biofuels,’ Bill Caesar, principal at consulting firm McKinsey told delegates at the BIO meeting in Atlanta, Georgia last month, ‘is to displace a meaningful proportion of petrochemical transportation fuels with renewable fuels that have a lower impact on the environment.’

However good these new second generation technologies are, meeting national government mandates on biofuels is going to require a lot of extra land, Caesar pointed out. In the US, the aim is to increase production of biofuels to 36bn/gallons/ year by 2022, while in Europe the goal is to replace 10% of transportation fuels with alternative energies including biofuels and electric vehicles. Worldwide, McKinsey expects that total biofuels consumption will triple from the current 20-25bn gallons/year to 65-70bn gallons/year in 2020 – a feat that Caesar says will require an estimated 40-45m ha of land to produce biofuels, double the amount used in 2008.

Indeed, so great is the ‘threat’ of biofuels production that The Nature Conservancy has now established a special working group to tackle the issue, says the organisation’s Jimmie Powell. Figures from TNC show that to generate the power of a 1000MW nuclear plant, operating 90% of the year, would require either 250 to 1000 acres in the case of nuclear, 350 to 2500 acres for fossil fuels, a 200 000 acre wind farm or a staggering 1.7m acres of dedicated energy crops.

‘We need these renewable sources of energy to prevent significant global warming,’ Powell says. ‘But avoiding climate change will require a lot of energy change and this has very significant land use implications.’

Second generation technologies will help to lower the impact by increasing the yield of biofuels generated per acre since every bit of the plant will be used. Every tonne of biomass produces between 80 and 100 gallons of bioethanol, according to Jack Huttner, vp commercial and public affairs at DuPont Danisco, while the best yields of biomass will come from dedicated energy crops such as switchgrass or miscanthus, he adds – tall, fast-growing plants that can often also be grown on marginal lands that would otherwise be unsuitable for the production of other crops.

‘Switchgrass we think is a real winner. It takes about three years to establish. Once you establish it, it’s good for six years. There’s very low inputs in terms of water and nutrients etc, so it makes a lot of economic sense. But a farmer has to commit two to three years in advance of first, significant yield.’

However, estimates about the amount of biomass produced per acre vary widely. Energy crop company Ceres recently reported that average biomass yields from US field trials of its switchgrass seed varieties were as much as 50% more than the US governments projected yields for 2022. It notes that one switchgrass variety grown in Califonia yielded a staggering 19t/ acre. These figures are much higher than a recent Sandia National Labs study which estimates 6t/acre for energy grasses, similar to figures from the US Environmental Protection Agency.

The first commercial-scale second generation plants are set to come onstream at the end of 2010, with 30 more set to begin operations in the US over the next few years, according to the US Biotechnology Industry Organization (BIO). The two main types of process operate either by direct biochemical or fermentation processes, which use enzymes to digest and convert the plant sugars to alcohols, or by thermochemical technologies that first apply heat and pressure to gasify the biomass to make syngas – a mixture of carbon monoxide and hydrogen – before it is converted to fuels.

Which technology is adopted will depend largely on the available feedstock, says Geraint Evans, fuels and energy manager at the UK’s National Non-Food Crop Centre (NNFCC). In countries such as the UK and other parts of Europe, the advantage of the thermochemical approach is its feedstock flexibility, Evans continues. Companies using this route can use not only waste agricultural matter, but are also able to make fuel from a range of other waste organic matter – including tyres, paper and cardboard waste and even food leftovers – that would otherwise be left to decay in landfill sites.

Ineos Bio, one of the frontrunners in thermochemical technology along with Range Fuels and Coskata, is aiming to have its first commercial plant onstream by 2011 and will make a decision on where to site this – either in the US or EU – by the end of this year. ‘We’re initially trying to prove different supply chains in the US versus the EU,’ says Graham Rice, external relations and development manager. ‘In the US there is an abundance of vegetative biomass, so very large scale plants are envisaged. The EU has less concentrated agricultural waste, but instead has high concentrations of people producing a lot of organic waste and strong legislation to divert this biodegradable waste from landfill. MSW is more challenging as a feedstock, but it provides opportunities for smaller scale, localised plants that address both the local waste issue and the need for clean, green biofuel.’

Like many other second generation processes, the Ineos Bio process also generates its own heat and power; a small commercial Ineos Bio plant generating 30,000t/ year of bioethanol would be expected to export around 6MW of power, Rice says. The fermentation step, using naturally occurring bacteria, progresses at around body temperature and ambient pressure.

But despite their low running costs, the initial costs of ethanol production from second generation plants are likely to be relatively high. Brazilian sugar cane is currently the cheapest biofuel at around $60/bbl, but next generation bioethanol prices will be considerably higher at least until many of the processes and technologies are optimised, says NNFCC’s Evans. ‘Second generation plants are expensive to build but cheap to run which is the opposite of what we have today with first generation plants.’ A typical first generation plant can cost anything from £50m for a small biodiesel facility to £300m for a state of the art world scale wheat ethanol facility, he estimates, against £200m to £600m for a second generation facility.

According to biofuels experts at the US Department of Energy, ‘Based on today’s technology, our mathematical models estimate that cellulosic ethanol produced via the biochemical pathway using corn stover as the feedstock will cost $2.61/gallon (in 2007 dollars, assuming a mature technology).’ This is much higher than ethanol produced by first generation plants, which currently averages around $1.65/gallon from corn starch, but this figure should come down to $1.49 by 2012, DoE researchers say – equivalent on an energy basis to a production cost of $2.22/gallon of gasoline. (Ethanol provides roughly 67% of the energy content of gasoline.)

The main factors in determining the costs of ethanol produced biochemically are the costs of feedstocks, pre-treatment, enzymes and fermentation organisms, according to the DoE – many of which are already seeing rapid improvements. Enzyme manufacturer Novozymes has recently announced, for example, that it has halved the cost of enzymes for the conversion of cellulosic material, says Lars Hansson, president, Novozymes North America. ‘And we plan to do that again in 2010 so we will be ready with commercially relevant volumes and prices as the industry develops starting in June 2010.’

Low cost ‘waste’ feedstocks will also be helpful in bringing down costs; however, they can’t be relied upon forever, warns Gerson Santos, director R&D corporate at Abengoa Bioenergy. ‘We cannot count on using a low cost waste because it’s going to be a commodity at some point.’ Ultimately, Santos says that biofuels producers ‘are going to enter into a carbon-constrained environment and will be rewarded for reducing carbon. If that doesn’t happen, if you don’t have an incentive to reduce carbon in the transport sector then you are going to be merely competing on price.’

Further in the future, meanwhile, biofuels experts point out that most facilities will also operate as biorefineries that produce a whole range of other renewable chemicals besides fuel. Some of these biofuel side-streams could be more valuable than the fuels themselves. ‘We see biorefineries evolving just like oil refineries did,’ says Brent Erickson, executive vp of BIO. ‘So when they first made gasoline for the Model T, now they make a whole range of products. We see that happening with biorefineries as well.’

For now though, the real challenge is not technology integration, it is supply chain development, says Jack Huttner, vp commercial and public affairs at DuPont Danisco. ‘The requirement of biorefineries for biomass is significant and organising the farmer producers to deliver the kinds of volumes we’re going to need is a big challenge.’

‘Building a biorefinery is going to cost north of $250m. We can’t move it once it’s built if all of a sudden farmers decide they are going to grow asparagus or something.’

Making sure that the correct infrastructure is in place is another challenge. Ethanol cannot be distributed in the existing petroleum gasoline pipeline system which poses a significant problem for suppliers. Alternative biofuels such as biobutanol have the advantage of having hydrocarbon-like properties that mean they can be sold directly to refiners and use the existing infrastructure, says Patrick Gruber, ceo of Gevo, which is aiming to commercialise its biobutanol technology by 2011. ‘The more interesting part of the story actually is that if you take the isobutanol, do a little chemistry to it, then you can make renewable gasoline. This is exactly gasoline, it meets the ATSM spec,’ he continues.

Car manufacturers could also help by making all new models flex-fuel vehicles, able to run on gasoline or blends of up to 85% ethanol, adds McKinsey’s Caesar. ‘I don’t know why every vehicle today isn’t a flex fuel vehicle. It costs just $200 extra to make them.’

Ultimately, Caesar continues, the real sustainability of biofuels will be judged on a complete ‘well to wheel’ analysis that takes in all their inputs and emissions – including fertilisers, water, power consumption power and the impact on land and biodiversity – compared with conventional gasoline. ‘Biofuels can contribute to reducing environmental impact but only if you produce them in the right way with the right feedstocks in a truly carbon reducing manner. I believe biofuels are going to be important but biofuels done wrong can create problems. Not every biofuel will pass the test.’

Biofuels manufacturers, meanwhile, argue that there is plenty of land available to grow all the energy and food crops needed. Biotechnology is already bringing big increases in crop yields, as well as developing plants capable of thriving on land that would otherwise have been left idle, they point out.

In the US, to produce the huge quantities of biofuels needed, ‘every region of the country will have a different model and a different feedstock. It could be wood, it could be dedicated energy crops, it could be sweet sorghum. In the MidWest it’ll probably be corn residue.’ Erickson says. ‘All of these choices will have to be made in the context of an overall set of criteria of sustainability, Gruber adds. ‘There is no one general rule and answer.’

‘If you start talking internationally, then the best place to grow biomass is in the tropics because there biomass is growing 365 days a year,’ adds Abengoa’s Santos, pointing in particular to Brazil as an area where he believes even more biofuels could be sustainably produced.

The 40-45m ha of land needed globally to produce biofuels, meanwhile, would account for only 3% of all arable land, Caesar reflects, adding that ‘we are at 1.5% today…With increased crop yields, this is not the sort of change that would result in a meaningful impact on crop production – but it is a lot of land!’

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