By Al Greenwood
HOUSTON (ICIS)--The first large-scale cellulosic plants are putting vastly different processes to work as they begin operations, in what could be the first successes after years of investment and failure.
Rentech abandoned its plans for a biomass plant, and the company is now focusing on producing nitrogen fertilizers from natural gas.
The latest plants to begin operations could have better luck, as they use different processes to convert biomass into fuel.
Its $130m (€99m) plant in Florida has a capacity to produce of 8m gal/year (30m litres/year) of ethanol.
KiOR's plant in Columbus, Mississippi, relies on a modified fluid catalytic cracker (FCC) that can uses biomass to produce drop-in fuel.
The plant began regular shipments of gasoline and diesel on 28 June. It has a capacity of up to 13m gal/year.
Another company, Cool Planet Energy Systems, is relying on a pyrolysis process to convert biomass into drop-in fuels and char.
Cool Planet is proceeding with plans to build three biomass-to-fuels plants in Louisiana. Each plant will have a capacity to produce 10m gal/year. The first plant should start production by the end of 2014.
The plant will extract sugars from stover, cobs and other leftovers of corn production. Those sugars will be fermented to produce ethanol.
Abengoa Bioenergia is also building a plant that will produce ethanol by fermenting sugars, extracted from biomass via enzymatic hydrolysis. The 25m gal/year plant should start up by January. It will consume nearly 350,000 tons/year of biomass.
Fermentation and the other processes all come with their own challenges.
Biomass is made up of lignin, cellulose and hemicellulose. Lignin needs to be separated from cellulose and hemicellulose, a challenge in itself, said Rick Elander, biochemical conversion platform manager for the National Renewable Energy Laboratory (NREL).
Fermentation-based producers then must hydrolyse hemicellulose and cellulose to produce simple sugars. Microorganisms then convert the sugars to biofuels.
Producing cellulosic sugars is a bottleneck, said Sam Nejame president of Promotum, a consultancy focused on renewable fuels and biobased chemicals.
Companies are attacking sugar extraction from multiple angles. Most rely on enzymatic or acid hydrolysis. One company, Renmatix, is developing a process that uses supercritical water to extract the sugars.
Sugars extracted from cellulosic materials are a blend of C5 and C6 monomers. Most microorganisms metabolise C6 sugars, while fewer consume C5.
These C5 sugars could make up a third to 40% of the total amount available from cellulosic feedstock, Elander said.
Some companies are tackling the problem by engineering microorganisms that can consume both types of sugars, Elander said. However, these dual-sugar microorganisms are not as robust as those that consume C6 sugars.
Once the sugars are extracted, the producers are left with lignin, which currently has little use beyond a boiler fuel.
In addition to fuel, fermentation also produces carbon dioxide (CO2) − about 1lb of gas for every 1lb of ethanol, Nejame said. Like lignin, this lowers yields, since the carbon from the feedstock is converted to a gas and not a fuel.
In fact, the Poet-DSM plant will use about 25% of the available material, leaving the rest to be used for erosion control and nutrient replacement, the company said.
The company received a grant worth up to $76m from the US Department of Energy (DOE), but the project was still unsuccessful.
The plant was closed and later sold to LanzaTech.
Rentech was developing a gasification and Fischer-Tropsch route before abandoning the project to concentrate on producing nitrogen fertilizer as well as wood chips and pellets for power plants.
In the past, gasification had struggled with tar formation, inorganic impurities and irregular proportions of gases being produced, according to an article by the MIT Technology Review, published by the Massachusetts Institute of Technology.
Nejame noted that gasification is also sensitive to the types of biomass being used as a feedstock, since these can affect operating conditions. The plants themselves consume a lot of energy.
Cool Planet uses a milder pyrolysis process to produce fuels.
The process, though, does not convert all of the biomass into fuel. Some of it is also made into char, which is not used as a fuel for automobiles.
Meanwhile, KiOR's FCC process has not met initial expectations.
In May, KiOR expected that fuel production at its plant would be 300,000-500,000 gal, keeping the company on track to produce 3m-5m gal of fuel in 2013.
However, KiOR disclosed on 8 August that Q2 fuel shipments at the facility reached only 75,000 gal.
A shareholder has recently sued the company, alleging it misled investor. KiOR is fighting the lawsuit, and the case is pending.
The industry, though, is still young, said Paul Winters, director of communications for Biotechnology Industry Organization (BIO).
"It just takes a lot more time and money than people imagined at first," he said.
For example, markets could develop for char and lignin, the byproducts of some of the processes.
The Department of Energy listed several possible uses of lignin in a study released in 2007.
Cool Planet is marketing its char as a soil additive, since the material is porous, allowing it to retain moisture and nutrients for plants.
As the renewable fuels market matures, Winters does not expect one process to dominate.
Companies are relying on a variety of technologies because they are using a variety of feedstock.
"Everybody is looking to pair a technology with a feedstock," Winters said. "I don't think there is going to be any single dominant player in the near future, at least."
Sam Nejame of Promotum said some companies are also developing hybrid processes that use renewable and petroleum-based feedstock. He noted that KiOR's process consumes hydrogen reformed from natural gas.
"While everyone talks about KiOR being strictly a renewable, the reality is it's a hybrid," he said.
Coskata, once in the gasification camp, is now using methane to produce syngas feedstock for its ethanol-producing microorganisms.
Other fermentation-based companies such as Calysta Energy are taking advantage of the wave of unconventional gas and developing processes that use methane as a feedstock, Nejame said.
"The availability of NGLs and inexpensive gas has really moved the horizon," he said. "It impacts everything."
Meanwhile, fermenting sugars could result in products well beyond ethanol, said Elander of the NREL.
Already, companies are relying on fermentation to produce isobutanol, a gasoline blendstock with a higher energy content than ethanol. Since isobutanol is hydrophobic, it lacks many of the problems associated with ethanol.
Fermentation could also produce chemical intermediates such as succinic acid.
The sugars themselves can be used as a feedstock for chemical reactions, Elander said. There is even research into producing carbon-fibre type products from sugars and lignin.
"There is a whole variety of possibilities beyond fuels," he said.
($1 = €0.76)
Follow Al on Twitter