A key reason why biomass is not more widely used is that it's difficult to standardize for size and moisture content. Handling and processing systems are feedstock specific and do not easily accommodate switching between different types of biomass such as wood chips, switch grass, walnut shells, shredded paper, etc. That's why the first step in any biomass-based process involves working out the problems involved in preparing, storing and handling substantial quantities of feedstock. In the case of B2M, our primary feedstock is forest waste, and we decided to initially go with a tractor mounted Power-Take-Off (PTO) style chipper. This would allow us to use readily available farm equipment to produce experimental quantities of wood chips in a form that's suitable for gasification.
It's in the nature of this type of applied engineering that as the development proceeds from one step to the next, the work done in the preceding step has to be revisited to ensure that it can simply be enlarged and still function effectively at the increased scale. Usually it can, but sometimes not. For example, while a tractor driven PTO chipper is appropriate for processing woody biomass through Step Four, the transition to Step Six will require stepping up to a tub grinder design that's capable of handling tons of forest waste a day.
Starting in 2008, Windward joined the open-source Gasifier Experimenter's Kit (GEK) Project based out of All Power Labs in Berkeley, CA. As one of their early adopters, we went down and welded together the fourth GEK to come out of their workshop. Over the years, we've returned and regularly upgraded our unit to incorporate improvements in design. We're currently on our fourth GEK iteration, and are reliably producing engine-grade gaseous fuel from the woody biomass grown in Windward's forest.
The conversion of wood gas--first into synthesis gas, and then into liquid fuels--involves the compression of a mixture of hydrogen and carbon monoxide. The safe compression of these gases requires a special built, leak-proof compressor. Windward is currently working on assembling a multi-stage, hydraulically driven, computer controlled, four-stage compressor capable of delivering the range of pressures needed.
Initially, we're compressing air, a focus which allows us to master many of the intricacies inherent in the compression process before adding the complexity of working with more challenging gases. A key guiding principle for B2M involves focusing on the equipment and materials found on working farms throughout the country. Farm scale equipment does entail a degree of risk, but the dangers are well known and routine. The decision to focus our initial work on compressed air is an example of this cautious approach.
Windward already has equipment capable of compressing small quantities of air up to 3,000 psi. This is relevant in that highly compressed air is the most benign way to store the energy derived from the gasification of woody biomass in a form concentrated enough to power a vehicle
This is where things get especially interesting. The specific liquid fuel that the B2M Project will initially focus on is methanol, a biogenic fuel that is a natural part of the environment. Not only is methanol a necessary ingredient in the production of bio-diesel, it can be used in place of exogenic fuels such as gasoline in flex-fuel passenger vehicles.
While a gallon a day may not seem like a lot, it's adequate to meet Windward's current on-site need for fuel. Reaching this level of production will signal that the project has solved the majority of the technical issues involved in the village-scale conversion of woody biomass into transportation fuel.
This is where things get especially interesting. The specific liquid fuel that the B2M Project will initially focus on is methanol, a biogenic2 fuel that is a natural part of the environment. Not only is methanol a necessary ingredient in the production of bio-diesel3, it can be used in place of exogenic fuels such as gasoline in flex-fuel passenger vehicles.4 While a gallon a day may not seem like a lot, it's adequate to meet Windward's current on-site need for fuel. Reaching this level of production will signal that the project has solved the majority of the technical issues involved in the village-scale conversion of woody biomass into transportation fuel.
There are two primary chemical routes that Windward is working on for the conversion of synthesis gas into methanol. The first is the Liquid Process Methanol reactor (LPMeOH) developed in the 1990s by Eastman at their Kingsport, TN, demonstration plant.
The second route involves the work done by Dr. Mahajan5 of the Brookhaven National Laboratory (BNL) involving a dual-catalyst, dual solvent reaction that proceeds at low pressure and low temperature. The nature of this reaction is such that it appears to be well suited for village scale production. Windward has entered into negotiations for a license from BNL to develop small scale applications of the technology.
This step will also require stepping up the sophistication of the gasification side of the operation. The initial work uses air to produce a fuel-grade gas suitable for powering the internal combustion engine that drives the compressor. Since fuel-grade gas is created using air as the oxidizer, about half of the gas produced is nitrogen, an inert gas that takes up space. This high proportion of inert nitrogen renders raw wood gas unsuitable as a feedstock for a synthesis reaction.
It's at this point in the process where we'll begin gasifying woody biomass in two steps using a two stage gasifier; the first stage converts the biomass into a combustible gas before the second stage (called autothermal steam reformation) maximizes the amount of reactable gas. The first stage converts woody biomass into charcoal and a tarry gas suitable for burning.6 Then this tarry gas, along with oxygen and steam, is "polished" in a second stage by passing it through a fluidized bed of glowing charcoal.7 This step breaks down the tars, water and complex molecules into synthesis gas, i.e. a mixture of carbon monoxide and hydrogen suitable for synthesizing methanol and other fuels.
It's an axiom of engineering that increasing the size of a process by an order of magnitude warrants a complete reexamination of each step in the process. Once the demands involved in expanding production by a factor of ten are resolved, B2M will be able to generate enough fuel to support a range of community activities such as transporting value-added products and produce to nearby urban markets, gleaning from local food processing sheds and orchards, gathering wild food resources such as elderberries and mushrooms, etc.
As transportation fuels become ever more expensive and intermittent, those who can produce their own transportation fuels will gain a crucial competitive advantage. Windward was intentionally located midway between Portland, OR, and the Yakima Basin. Portland is a city complex with more than a million hungry consumers. The Yakima Basin is a huge food-producing region served by a series of Columbia River dams that provide both the water needed to grow food in the desert and the electricity needed to get it to the crops. By being able to produce its own transportation fuels, Windward will be well positioned to function as an intermediary between Yakima's producers and Portland's consumers.
When this level of production is achieved, the community will be able to start marketing fuels to neighboring farms. For example, since Windward is located in a region known for its wheat production, growing wheat is not a good use of Windward's time and talent. It would be to our advantage to produce the fuel needed to power our neighbor's tractors and harvesting combines. In effect, B2M will give us the ability to trade fuel for wheat. Building on the ability to meet most of our core needs ourselves, this level of production will enable the community to purchase goods and services it will need to maintain itself, improve its quality of life and then go on to create sister communities.
Using the skills developed in Step Six, the next stage involves the construction of portable plants housed in standardized shipping containers. These mobile facilities can then be moved into the forest to address the dangerous build up of woody biomass, a service that is especially needed in areas affected by insect damage.
This work will supply jobs for environmental studies students in need of employment to pay off student loans. By providing seasonal live-in employment, graduates will gain work skills that can be used to save endangered forests throughout the country. The practice of forest fire prevention has created a situation in which the build up of fuel threatens massive fires capable of devastating large areas and habitats. B2M offers an effective way to counter that risk, put people to work and retain funds in local, rural communities.
1) It's important to remember that fuels do not produce energy; rather, fuels are simply ways to store, transport and then use energy at some later point in time. For example, air is all around us and is energy neutral, but when it is highly compressed, it can operate air-powered vehicles on property, power a wide range of tools, and serve as a way to balance out peak electrical loads.
2) In this case, biogenic refers to chemicals that are produced in nature and which can be easily broken down by biological organisms. This contrasts with exogenic which refers to compounds which do not occur naturally in nature and which are therefore not easily broken down by naturally occurring organisms.
3) It's ironic that the large scale manufacture of biodiesel currently relies on the use of methanol produced from fossil fuels.
4) Because breathing methanol vapors can cause serious health problems up to and including death, B2M looks to take methanol production one step further and convert it into dimethyl ether. DME is an almost ideal renewable fuel in that it can be used in both standard and diesel engines. Most people encounter DME because of its use as the propellant in hair spray.
5) see US Patent Application Number 2003/0158270
6) Woody biomass can generate three differing grades of fuel gas: burner, engine and synthesis. Burner grade gas contains small amounts of tarry substances that would harm an internal combustion engine, but pose no problem when burned to heat water or bake bread.
7) Oxygen is added to the gas stream to convert some of the char into carbon monoxide and heat the remaining char to incandescence. This heat also enables the char to convert steam and carbon dioxide into carbon monoxide and hydrogen, thereby increasing the gas's energy content.