The next two years will see the introduction of systems designed to allow refineries to produce gasoline and diesel from biomass. GTForum investigate
Ethanol production in the US has boomed on the back of government incentives and mandates, rising from around 1.4 billion gallons in 1998 to more than 13 billion gallons in 2010. However, ethanol as a product has several disadvantages from both a consumer and a producer perspective. From the consumer-side, ethanol is less energy-dense than conventional fuels, translating into a reduction in range and apparent miles to the gallon. From the perspective of a producer, ethanol’s corrosive nature creates headaches in terms of transportation, but also in limiting the amount that can be blended into gasoline and used by the current vehicle fleet.
That’s why catalyst developers and original equipment manufacturers have been looking at a different approach, producing “drop-in fuels” from biomass, which have all the greenhouse-gas and sustainability benefits of cellulosic ethanol, while being chemically indistinguishable from gasoline, diesel and other oil products derived from crude oil.
Two of the most promising projects in this area are UOP and Ensyn’s integrated biorefinery (IBR) pilot-scale project in Hawaii, and the IH2 project, led by the Gas Technology Institute (GTI),i with catalysts provided by CRI Catalyst.
Despite being pilot projects, both technologies are not far from commercialisation. Jim Rekoske, vice-president and general manager for Honeywell UOP’s Renewable Energy and Chemicals business, says UOP aims to be able to offer its system to customers for commercial sale in 3Q12, while the IH2 project is scheduled for commercial operation in 2014.
Vann Bush, managing director, energy conversion, GTI, told GTForumthat based on an analysis from the National Renewable Energy Laboratory (NREL), the anticipated cost on a product basis for fuel produced using the IH2 technology is around US$1.60/gallon for woody biomass, dropping to around US$1.36/gallon if a refiner has sufficient spare hydrogen capacity and opts to forego installing the reforming unit. This compares to the US Department of Energy’s goal of US$3/gallon.
Rekoske says around 85–90% of the costs associated with producing any transportation fuels are determined by the cost of feedstock, with the conversion process making up the remainder.
"Until demand in the industry grows and more feedstock sources are developed, we expect Green Jet Fuel will sell for 1.5–2 times the cost of petroleum-based fuels without any government support. While this is a premium, and may be more than some in the market are willing to pay, with government support and increased capacity throughout the value chain, we believe cost parity with petroleum-derived fuels can be achieved. The key to achieving this without support is growing the value chain to compete on the scale of commodities like petroleum," Rekoske says.
The balance of gasoline to middle distillates for both technologies is dependent on the feedstocks used for both technologies. Reskoske says UOP’s system sees around a 50:50 balance between gasoline and distillate, “probably in the range of 40:60, 60:40 at this point, but there are some molecules that come out of biomass that naturally fit into the gasoline range and some that naturally fit into the distillate range, and the challenge will be that you’re always adding cost if you try to fit those round pegs into square holes”.
In the case of the IH2 process, “there is an expectation that we’ll have some flexibility in moving the distribution between the higher boiling point and lower boiling point materials in the range of gasoline and diesel. That’s our intention, we haven’t demonstrated how much flexibility we can manage there, but we’re optimistic we can move the distribution around between gasoline and diesel fractions,” Bush says.
He also says woody biomass tends to produce more gasoline than diesel via the IH2 process, while algael fuels tend to produce more diesel. Overall yields are also affected by feedstock. “The yields vary between say 70 gallons per ton to 157 gallons per ton. The worst yields we’ve had are with fairly high ash agricultural residues and the highest are with algae.”
Rekoske is particularly pleased with the yields UOP has seen so far – in the order of 300 gallons of renewable fuel per tonne of triglyceride feedstock, obtained from oil seed crops, algae and fats and greases. Given that overall yields are highly dependent on feedstock, direct comparisons between different biomass to oil product technologies cannot be made unless they both use the same feedstock.
“We’re achieving yields from the conversion facility and from our testing and laboratories that are much, much, higher than what we had anticipated, approaching the theoretical limits. We just did not expect to achieve yields that were that high,” he says
With both technologies, the final product slate is largely independent of the host-refinery’s complexity. This might make such systems more attractive to low-complexity refiners in regions with high biomass potential.
Refinery integration
One crucial area where the two technologies diverge is with regard to their hydrogen demand. UOP’s system does require some input hydrogen, cutting the lifecycle emissions reduction from more than 95% to 85%, assuming the hydrogen is made from non-renewable sources. UOP’s process also produces fuel gas as a by-product that can be used for electricity generation or to provide heat for other refinery processes. In contrast, the IH2 technology is hydrogen-neutral, by virtue of using steam methane reforming of the light gases produced by the process.
The load on other utilities for both systems is fairly light. UOP’s system requires the use of a sour water treatment system, while Bush says IH2's waste water stream can be consolidated with refinery water treatment. The IH2 process also exports steam and a small water stream that is relatively free of carbon. In addition to the oil products produced by the process, Bush says it also generates a nitrogen/sulphur stream "which should have fertiliser value" and a char stream that can be used as a solid fuel or soil amendment.
In the future, there are two main options for refiners looking to use the IH2 technology. One involves the installation of both the main unit along with the components for conventional steam reforming/pressure swing absorption system, and the latter can be committed by a refinery with sufficient spare hydrogen capacity looking to reduce capital costs.
UOP is looking to develop the technology in a modular fashion to minimise construction costs, while Bush expects the IH2 technology to be built on a variety of scales. He expects that while many projects “would be at a scale that would be able to be fabricated in a shop and shipped to a site”, some “will be very large processing facilities and be built on site”. Bush says the scale would range between a few hundred tons per day to 2,000tpd “for most of the feed materials”.
One of the less technical issues that will require careful thought is that of physically sourcing so much biomass, due to its poor energy density. “Until you start having to source 400 or 1,000 tonnes of biomass on a daily basis in a sustainable manner, I don’t think you realise what the challenges associated with moving all that material around are. It’s not the same as moving around a petroleum product, where one can build a pipeline or a supertanker and transfer it quite efficiently. It’s much less energy dense; hauling all that biomass around is a substantial challenge and we’re working with many partners to understand how to overcome those challenges,” Rekoske says.
However, both companies are optimistic about the promise of biomass integration in refineries. “We’ve grown more excited as the development has gone on, and we’re at a point where we’re going to be out publicly in the next few months discussing the technology in more detail and in earnest. It’s very difficult when you’re at the early stages of a pilot programme to know how excited you should be. Now we’re in the later stages, we’re very excited and we think other people will be as well,” Rekoske says.
“I’m really encouraged that we’re doing something that has the potential to compete without the requirement of subsidy. I think that’s very interesting and compelling, and because it has so much flexibility in terms of feed, it’s a solution that has application globally… I think our operational experience is also encouraging me. This is not a very, very complex process, it's pretty simple, so I think it has a lot of qualities that will make it a reliable process in the field, and that’s what counts. I’m optimistic,” Bush says.
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