Wednesday, January 2, 2013

Turning forest waste into biochar

Too much biomass waste in tundra and boreal forests makes them prone to wildfires, especially when heatwaves strike. Furthermore, leaving biomass waste in the forest can cause a lot of methane emisions from decomposition.

In order to reduce such methane emissions and the risk of wildfires, it makes sense to reduce excess biomass waste in fields and forests. Until now, this was typically done by controlled burning of biomass, which also causes emissions, but far less than wildfires do. Avoiding wildfires is particularly important for the Arctic, which is vulnerable to soot deposits originating from wildfires in tundra and boreal forest. Such soot deposits cause more sunlight to be absorbed, accelerating the decline of snow and ice in the Arctic.


A team of scientists at University of Washington, sponsored by the National Science Foundation, has developed a way to remove woody biomass waste from forests without burning it in the traditional way. The team has developed a portable kiln that can be assembled around a heap of waste wood and convert it to biochar on the spot, while the biochar can also be burried in the soil on the spot.

Demonstration in Kerby, Oregon,
Nov. 6, 2012, 
 by Carbon Cultures
Credit: 
Marcus Kauffman at Flickr
The team initially started testing the effectiveness of a heat-resistant blanket thrown over woody debris.  The team then developed portable panels that are assembled in a kiln around a slash pile.

Students have set up a company, Carbon Cultures, to promote the technology and to sell biochar. CEO of Carbon Cultures is Jenny Knoth, also a Ph.D. candidate in environmental and forest sciences.

The kiln restricts the amount of oxygen that can reach the biomass, which is transformed by pyrolysis into biochar. The woody waste is heated up to temperatures of about 1,100 degrees Fahrenheit (600 Celsius), as the kiln transforms some 800 pounds of wood into 200 pounds of biochar in less than two hours. “We also extinguish with water because it helps keep oxygen out and also activates the charcoal [making it more fertile in soil].”

Currently, the total costs of disposing of forest slash heaps (the collections of wood waste) approximate a billion dollars a year in the United States, according to Knoth.

And of course, adding biochar to the soil is a great way to reduce carbon dioxide levels in the atmosphere. “Biochar is proven to fix carbon for hundreds of thousands of years,” Knoth said.
Demonstration in Kerby, Oregon, November 6, 2012, organized by Carbon Cultures Credit: Marcus Kauffman at Flickr

As said, when biomass waste is left in the open air, methane emissions are produced during its decomposition. Moreover, such waste will fuel wildfires, which produce huge amounts of emissions. The traditional response therefore is to burn such waste. Pyrolyzing biomass produces even less greenhouse gases and less soot, compared to such controlled burning.

Biochar is produced in the process, which can be added to the soil on the spot. This will help soil retain moisture, nutrients and soil microbes, making forests more healthy, preventing erosion and thus reduces the risk of wildfires even further, in addition to the reduction already achieved by removal of surplus waste.

A healthy forest will retain more moist in its soil, in the air under its canopy, and in the air above the forest through expiration, resulting in more clouds that act as sunshades to keep the forest cool and return the moist to the forest through rainfall. Forests reinforce patterns of air pressure and humidity that result in long-distance air currents that bring moist air from the sea inland to be deposited onto the forest in the form of rain. Finally, clouds can reflect more sunlight back into space, thus reducing the chance of heatwaves.

References

Recycling wood waste - The Daily of the University of Washington
Helping Landowners with Waste Wood While Improving Agribusiness and Energy - National Science Foundation

Related

- Biochar
- CU-Boulder gets into biochar

5 comments:

  1. Addition of biochar to soil is the simplest way to sequester CO2 emission, and for the common man to participate in trying to keep the Earth alive.
    Right after stopping use of oil and coal that are so intrinsic to money making and present way of things and land abuse. But those are passive by default simply because oil use and land abuse are so engrained in modern life, everything the touch of money touches seems to weather badly and decay.
    My input at highest level to save earth would be to encourage a 'Act of God' alteration to the value of money to align it to Earth alive.
    But my hands need doing something that I can see. To feel I've accomplished something and peoples I'm sure with the state of things coming are going to need something to do that keeps the mind clear and to be actively trying to reverse what has already been done to Earth.

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  2. Where are the specs for this kiln?

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    1. The kiln has a heating range from 400- to 600-degrees Celsius; 30% of the wood mass converts to biochar; 70% evaporates into steam and other gases, leaving behind little waste.

      The kiln pictured in the post is five-feet tall, allowing it to be easily transported and put up elsewhere. It can take relatively large blocks of wood; larger pieces can be cut to size with electric chainsaws that can be connected with a cable to battery packs that can be carried in a belt or a backpack and that can be recharged on location with portable solar panels or with power from the batteries of electric vehicles.

      “We’re scaling up the technology to approach the Pacific Northwest forests with something of the size we need,” Knoth said.

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    2. So how do you operate it? What fabric are you using?

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    3. The research team started out with heat-resistant material to cover biomass waste, referring to it as a pyrolysis blanket. After testing, they found that it worked better when shaped as a kiln, using metal angles and clamps to keep it closed. Further testing is taking place to find out what are the best shapes and materials and the best ways to operate the kilns.

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