Food Engineering

Engineering R&D: Gen II for biofuels

May 1, 2011
Commodity prices and a credit crunch sidelined the first wave of biofuel plants, but process inefficiencies also played a role. The next generation of ethanol producers won’t make the same mistake.

Kamla Jevons, European business development manager-food & life sciences, Koch Membrane Systems, Stafford, UK. Source: Koch Membrane Systems.

Ethanol production from corn rubbed a lot of people the wrong way. Increased demand contributed to higher prices for cereal makers, livestock operators and producers of high-fructose corn syrup, and the use of food for fuel struck many as morally wrong. The sin of inefficiency also contributed to the closings, cancellations and mothballing of many of the biofuel plants: By focusing exclusively on the end product and treating the many byproducts as waste to be sold off as animal feed, the facilities simply did not exploit the economic possibilities of production. Consequently, investors were left with overcapacity (tripled in four years, according to the Renewable Fuel Association) and a building bust (10 plants under construction or expanding as of January, compared to 76 in 2007).

However, ethanol production isn’t going the way of New Coke. In January, Agriculture Secretary Tom Vilsack announced $405 million in loan guarantees for three biorefinery projects in Alabama, Mississippi and Florida. The feds aren’t doubling down on ethanol, however: The funding is for integrated biorefineries that use wood chips, solid municipal waste and other cellulosic materials as their raw materials. If the projects are to attract investors, they also will need to capitalize on the full value of their processes.

Second generation biofuel installations are just beginning to emerge from the pilot and demonstration plant stage, and shifting market conditions will have as great an impact as they did on the first generation. But these newer facilities also integrate technologies such as membrane filtration. The basic process-convert starch to sugars, then ferment the sugars to produce alcohol for distillation-is the same, but value will be extracted at key junctures to maximize value and financial returns. And that change in approach is keeping people like Kamla Jevons busy.

Jevons is the European business development manager for Koch Membrane Systems (KMS) in Stafford, UK. A graduate of London’s West Middlesex College with a Higher National Diploma degree in electronics engineering, she has been involved with membrane applications for a quarter of a century, the last 10 years with KMS. Jevons has expertise in ion exchange, chromatography and membrane separation, beginning with high-purity water production and extending to fermentation-based products, using reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) and microfiltration.

Second-generation biofuel plants likely will include ultrafiltration, nanofiltration and reverse osmosis technology to maximize recovery of valuable elements that currently are discarded as animal feed or waste. Source: Koch Membrane Systems.

FE: Why haven’t Gen I ethanol plants panned out?

Companies that put together the base technology were saying, “Here’s a refinery-in-a-box.” They were based on the petrochemical industry’s approach, and the focus was strictly on the ethanol produced. A chemical engineer is comfortable with centrifuges and evaporation but not with fine separation technologies, so the byproducts were viewed as waste or animal feed. The nearest the first generation plants got to finite separation was water recovery and reuse.

There were all sorts of recoverable materials that could have improved those plants’ financial viability. Plant proteins aren’t of interest for biofuel, but instead of disposing of the protein as feed after it’s been denatured, membrane separation could remove it early in the process, when it has more value. Similarly, lactic acid and other organic acids that are byproducts of fermentation can be recovered for use in the production of additives for biodegradable plastics. Those acids already provide a level of biodegradability to polylactide (PLA). They also can provide biodegradability to PET and other plastics.

FE: How will membrane separation be incorporated into the new generation of biofuel plants?

This is an evolving area, and confidentiality surrounds virtually all of our work, but generally speaking, techniques are being considered to facilitate movement to continuous fermentation, rather than batch. Filtration techniques are being evaluated for their ability to improve recovery, reduce waste and lower energy costs. For example, ultrafiltration can clarify the process stream after conversion to sugars during the saccharification process.

Some of the cellulosic biofuel processes use acid/alkali to extract fermentable material from stock such as corn stover. In that case, nanofiltration can be used to recover and concentrate some of the useful sugars like hemi-cellulose, which also is used in the fermentation process.

FE: Which regions of the world are leading the movement toward cellulosic biofuels?

There is activity in every region, though programs are dependent on what is grown there. In Scandinavia, for example, technology based on wood chips is being developed because that’s their feedstock. There are seven or eight major biorefineries currently operating in the European Union and producing multiple products.

A huge amount of money is being made available by the US government for research and investment in biofuels and integrated biorefineries, much of it focused on increasing product recovery, reducing waste, lowering energy costs and improving greenhouse gas profiles. In 2009, the US Department of Energy committed up to $564 million for pilot-, demonstration- and commercial-scale, integrated biorefinery projects. Membrane technology will be part of many of these projects.

FE: Can older ethanol plants be retrofitted to add value?

Nano (NF) and UF can be inserted into a conventional biofuels process to enhance recovery. A centrifuge is the first clarification step to remove dead yeast cells and proteins. The closest Gen I processes have gotten to fine separation is the insertion of RO after centrifugation and before evaporation, with condensate recycled to fermentation, thereby reducing on-site water usage.

FE: How has the technology improved to make it more feasible for use?

Filtration in water treatment has experienced perhaps the greatest improvement. Years ago, those membranes had a useful life of 12-24 months. Today, some last four to six years. The technology is well understood.

Similarly, the understanding of how NF works is much greater than it was 15 years ago. NF separation is one of my passions. There is no such thing as the ideal NF membrane; they all have different separation characteristics and different functions. Perhaps the membranes themselves have not changed dramatically, but the understanding of the chemistry of the membrane and the fluid stream itself has advanced considerably.

FE: If separation and filtration are developed for biofuels, might there be some process transfers to food application, such as dairy applications?

Compared to biofuels and other industries where filtration and separation are still novel, dairy’s use of membranes is well understood. UF is standard and has gone through a long learning curve. The growing areas in dairy are NF and RO, whether it is for enhancing product-stream processes or for producing new products. In the UK, microfiltration now is being used to cold-pasteurize milk, and NF and RO are being used to produce low-lactose milk or to concentrate other components.

FE: Do any comparisons support the contention that filtration technology will save biofuel operators money?

As a complement to evaporation, RO definitely provides some economic advantages, particularly over time. RO is limited in how much it can concentrate, perhaps 20 percent solids compared to 40 percent with evaporation. But the initial capital costs are lower by about a third compared to three-effect evaporation. Over five years, capital and operating costs are less than a third.