Commercialization of renewable-resource-based routes to chemicals is gathering speed, with major players such as Dow and Dupont already actively involved. Now, studies done at Utrecht University, Utrecht, the Netherlands, indicate that biofeedstocks can play a far wider role and offer significant economic and environmental advantages for producing many bulk chemicals.
The studies focused on 15 chemicals — acetic acid, acrylic acid, adipic acid, butanol, caprolactam, ethanol, ethyl lactate (EL), ethylene, lactic acid, lysine, 1,3-propanediol (PDO), polyethylene terephthalate (PTT), polyhydroxyakanoates (PHA), polylactic acid (PLA) and succinic acid — that realistically could be produced via fermentation and that have substantial potential consumption, at least 200,000 metric tons/year in Western Europe, explains Barbara G. Hermann of the school’s Department of Science, Technology and Society. An industrial panel, drawn from companies including BP, Degussa, DSM, Dupont, NatureWorks, Novozymes and Shell that are in a consortium supporting the research, were involved in the selection. Some of the firms also contributed data from their own large-scale bio-based plants and provided expertise, such as for estimating plant costs.
The first study, which appeared in 2007 in Applied Biochemistry and Biotechnology, analyzed the economics of production using biofeedstocks versus oil or natural gas. Valid comparisons could be drawn, Hermann notes, because she developed a generic approach that allowed all processes to be put on a common basis. Fermentation-based routes included both current technology and what may be possible in the future (assuming continuous fermentation and higher yields, 90 mol.% of the theoretical maximum, because of better genetically engineered micro-organisms).
The analyses, based on constructing a new 100,000-mt/y plant in Western Europe, gave a profited production cost, akin to a market price, for each chemical for each route. She evaluated its sensitivity to varying prices for sugar (70€/mt, 135€/mt, 200€/mt and 400€/mt) and crude oil ($25/bbl and $50/bbl), the nature of the sugar source (sugar cane, lignocellulosics and corn starch), as well as plant size (100,000 mt/y, as well as 200,000 mt/y and 400,000 mt/y for some of the products). The results showed that making many of the chemicals with biofeedstocks was already economically viable.
A second study focused on using a common methodology to assess the environmental impact — namely, greenhouse gas emissions and non-renewable-energy use — for the same 15 bulk chemicals over their entire life cycle. The results, recently published in Environmental Science & Technology, indicate that biofeedstocks provide significant savings compared to conventional petrochemical-based routes for most of the products — fermentation now doesn’t offer benefits only for adipic acid and acetic acid but eventually should (Figure 1). Indeed, Hermann adds that future fermentation technology may reduce greenhouse gas emissions by more than 100% when energy credits are considered.
Figure 1. Most bio-based routes provide reductions in greenhouse gas emissions. Source: Environmental Science & Technology.
Since the studies came out, Hermann has updated the results — to consider less optimistic scenarios for the performance of future fermentation technology and to account for higher prices of both crude oil and sugar.
As far as productivity, for example, she tested future performance for ethanol using 10 g/Lh instead of 50 g/Lh (versus current actual values of about 2.2 g/Lh for starch feedstock). This impacted investment, primary energy consumption and profited product cost by less than 5%. So, the general conclusions still hold, Hermann stresses.
“We actually recently looked at updated numbers for a crude-oil price of $70/bbl for a slightly reduced number of bulk chemicals… The outlook can be summarized as ‘the picture improves’ — even at the highest sugar price of 400€/mt, ethanol, succinic acid, PDO/PTT, PLA and ethyl lactate are economically viable,” she notes. “At 200€/mt, the list also includes acetone/butanol/ethanol and ethylene.”
The Utrecht University team now has evaluated economic viability, market size and environmental improvement together. “The results show that ethylene is best, followed by PHA, PLA and PTT (the latter three are on the same level). Market size is an important factor here, as the market for ethylene is very large, whereas the market may be much smaller for other chemicals.”
Prospects for biofeedstock-based bulk chemicals are favorable but Hermann raises a caution: “We have seen a coupling of sugar and oil prices, with both prices increasing significantly in the past year.” Several factors have contributed to this, including recent crop failures, economic growth in China and India, and competition with biofuels, she explains. “There are ambitious policy goals [for biofuels], whereas policies for biochemicals are still missing… policy action by governments can lead to improvements for biochemicals,” she stresses.