Saturday, October 23, 2010

Charcoal Biofilter Cleans Up Fertilizer Waste Gases

We have addressed biochar a great deal over the past three years.  A necessary step is the production of an active elemental carbon component through roasting using produced volatiles as a heat source as is done for charcoal.

An obvious interim step is to collect that biochar to use as a filter to remove gases.  Ammonia is ideal, but most gases are useful when adsorbed.  Such an effort could properly assist in redistribution of the product to the most damaged soils.

It is noteworthy that those in the field continue to fail to differentiate traditional wood char from what is called biochar.  Both products are produced using the same protocol and largely to the same temperature regimes and are thus assumed to be much the same thing.  This is misleading.

Charcoal is produced directly from wood in all its forms.  The end product is naturally coarse and difficult to break up and will retain its chunky nature for centuries.

Biochar is derived from annual, non woody plant waste that has dried enough to pass through the process.  Naturally dried back corn stover is particularly suitable and was used to support the production of terra preta for centuries in the Amazon.  Any dried plant waste can be thrown into the mix.  This produces mostly powdered elemental carbon that is easily incorporated into the soil.

It is also easily used as a filter product to support gas adsorption and should be preferred.  Once saturated, such materials can be best added back into the soil base along with additional soil conditioners.

Agriculture will be producing biochar as a matter of normal operations to sustain and improve soils.  Supplying that product to industry on a loan basis is a practical solution to much of the pollution tail of industry and it should end up been cheap.

Charcoal Biofilter Cleans Up Fertilizer Waste Gases

by Staff Writers

Washington DC (SPX) Oct 19, 2010

The Shahjalal team has now built a prototype biofilter for ammonia extraction based on wood charcoal in which the nitrogen-fixing microbe Nitrosomonas europaea has been grown.

Removing the toxic and odorous emissions of ammonia from the industrial production of fertilizer is a costly and energy-intensive process. Now, researchers in Bangladesh have turned to microbes and inexpensive wood charcoal to create a biofilter that can extract the noxious gas from vented gases and so reduce pollution levels from factories in the developing world.

Writing in the International Journal of Environment and Pollution, Jahir Bin Alam, A. Hasan and A.H. Pathan of the Department of Civil and Environmental Engineering, at Shahjalal University of Science and Technology, in Sylhet, explain that biofiltration using soil or compost has been used to treate waste gases for the last two decades.

There are simple filters for reducing odors and more sophisticated units for removing specific chemicals, such as hydrogen sulfide, from industrial sources.

Among the many advantages are the fact that biofiltration is environment friendly technology, resulting in the complete degradation by oxidation of toxic pollutants to water and carbon dioxide without generating a residual waste stream.

It also uses very little energy. Biofilters are widely used in the developed world but their use in the developing world which is rapidly being industrialized but not necessarily considering pollution control.

The Shahjalal team has now built a prototype biofilter for ammonia extraction based on wood charcoal in which the nitrogen-fixing microbe Nitrosomonas europaea has been grown.

This microbe derives all its energy for metabolism, growth, and reproduction from ammonia, which it absorbs and oxidizes to nitrite. The microbe is commonly found in soil, sewage, freshwater, and on buildings and monuments in polluted cities.

The team found that their prototype biofilter could function at an ammonia concentration of 100 to 500 milligrams per liter of gas and remove the ammonia from this gas stream almost completely. Approximately 93% removal of ammonia gas was seen within seven days.

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