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Liquid Wood, Anybody?

ImageOne of the most abundant forms of renewable energy available in the United States is wood residue from forestry operations. The carbon in wood residue is bound to go back to the atmosphere, either as carbon dioxide (CO2) as a result of combustion (natural or controlled fire), or through methane (CH4), as a result of decomposition. Methane is actually more than 30 times worse in terms of greenhouse effect, so burning wood is by and large better than leaving it there. If you capture the energy produced in the process, you have got a renewable energy source.

There are over 3,000 MWs of wood-to-energy power generation capacity in the U.S., about half of which is linked to industrial facilities (sawmills and paper mills), and half is stand-alone facilities. However, in the current economic environment of low electric demand, low gas prices, and uncertain renewable energy policies, stand-alone facilities are struggling to compete and attract financing, and industrial facilities are also struggling due to low wood products demand and offshoring.

So, what do we do with all this renewable resource? Well, how about liquefying the wood and using it as a substitute in old power plants that are currently fueled by residual fuel oil? Residual fuel oil is the heavier component that comes out of crude oil refining; unlike diesel and gasoline, it cannot be used for transportation and is therefore used mostly for power generation and for maritime engines. And it’s dirty.

Does it sound far-fetched? It’s not. The technology to make “liquid wood” has been around for a long time. It’s called pyrolysis and several companies have used for many years, using it mostly for other applications, or to chase the holy grail of converting biomass into liquid transportation fuels, which demand a higher price point, but create technological challenges. On the other hand, burning the liquid wood in a boiler for power generation is fairly easily accomplished, and it is even possible to use liquid wood in low-speed reciprocating engines with some relatively small modifications.

So, let’s do the math. The cost of procuring wood residue comes to about $ 3-4 / MMBtu in most parts of the country. Processing (pyrolysis) and transportation could be another $ 6-7 / MMBtu. So, can we sell this oil for more than $ 10 / MMBtu and turn a tidy profit?  Well, market prices for residual fuel oil, in 2011, were around $ 2 / gallon, or $ 13-14 / MMBtu, which is a nice spread, especially if you believe that basement low oil prices are not coming back any time soon.  And that price does not include the renewable energy value, which can be monetized through renewable credits and federal incentives and guarantees.

And where can this be done? Florida and Hawaii are big markets and account for the majority of the $ 3 billion / year U.S. residual oil market. Massachusetts, New York, and Virginia also show significant consumption. All of these states have abundant wood supplies, and Northern Florida has a vibrant forestry industry.

Stefano Ratti's picture

Thank Stefano for the Post!

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Paul O's picture
Paul O on Feb 8, 2012 1:58 pm GMT

The problem is that wood that falls to the ground in the forest and turns into CO2 and Methane is dispersed over a very wide Mega-Acreage of difficult to traverse, nearly impossible reach, wooded terrain, located in multiple states covering hundreds of square mikes. While the processing facilities are few and far between. In other words, the logistics are truely poor. Thgis is also true for standing trees.

This may sound negative, however it is the truth, however negative it might be. The logistic for for wood as a power supply fuel, on an industrial scale is just very poor.

Stefano Ratti's picture
Stefano Ratti on Feb 8, 2012 10:54 pm GMT


There is no question that the logistics of gathering wood as a power supply for fuel are challenging, and that biomass is bound to remain a small piece of the overall energy picture.

However, I am not suggesting to go after twigs/branches on the ground, dispersed over immensely large areas. Rather, it makes sense to use wood residuals only in places where you have a vibrant forestry industry with large industrial landowners (South-East and North-West). In those situations, you can access leftovers from harvesting operations at a reasonable cost ($3-4/MMBtu, including stumpage, loading, grinding, and hauling).That may still be too expensive for power generation, given the high capital and operating cost of a biopower facility, but, if you can use this fuel to replace more expensive petroleum-based products, it may start to be an acceptable cost.

In the South-East, where you have mostly pine plantations, you can get 10+ tons of wood residuals per acre harvested and there are also thinning operations that produce wood residuals. In the Northwest, where you have mostly douglas firs, you can actually get 30+ tons of wood residuals per acre harvested, but the topography may make it more expensive to extract. Closed loop (i.e. dedicated energy crops) is also a possibility, but that may be a little more expensive today ($4-6/MMBtu). There is also urban wood, trimmings, and material from wood processing facilties (chip mills, sawmills, and pulp mills).

I may write a separate piece on biomass supply chain economics, as it is an interesting topic.

Thank you again for your input


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