Environmental Remediation Using Biochar

Photo Credit

USDA Forest Service photo by Zhiyong Cai

A typical biochar composite board prepared in the Forest Products Laboratory.

Natural and human sources of pollution threaten freshwater resources and soil. One of the most cost-effective ways to clean water is using adsorbents that remove pollutants by attracting these contaminants to their surface.  

Biochar, which is made from pyrolyzing (i.e., burning without oxygen) woody materials, is an efficient, cost-effective, and environmentally friendly adsorbent that can be made from byproducts of active forest management.  Biochar is often present as a powder, however, which can make it impractical to use and difficult to recover after water treatment. 

Forest Products Laboratory scientists are investigating the use of biochar in removing pollutants from the environment. Notably, they have developed a process to form biochar composite boards to enhance the use of biochar for remediation. These biochar composite boards are made by gluing biochar particles with natural binding molecules, such as lignin, starch, carbohydrates, and tannins. These sustainable products, made entirely from biomass wastes, are patent pending. 

 Key Findings:

Photo Credit

USDA Forest Service image by Joshua Limbaugh and Dorothy Punderson

Cycle of production and function of biochar composite boards.

• Combining biochar with natural binders such as lignin into boards, or incorporating nanomaterials such as metals into biochar, can enhance the use of biochar for removing environmental pollutants from soil and water.
• Biochar composite boards show promise in removing mercury, lead, cadmium, chromium, and nickel from water.
• Biochar’s ability to adsorb lead can be improved by using pine wood residue that has been exposed to the environment for no more than six months and by treating the biochar with sodium hydroxide.
• Biochar can remove 95 percent of per- and polyfluoroalkyl substances (PFAS) from contaminated water in 1 hour and 97 percent of PFAS over 24 hours. 

Collaborating with the Southern Research Station, Forest Products Laboratory scientists are investigating properties of biochar that influence its quality and ability to adsorb heavy metals from the environment., They found that lead adsorption varied with tree species. Biochar made from downed loblolly pine left out in the environment 6 months adsorbed more lead than biochar made from pine that had been left out in the environment for 12 months. These results and related research can optimize the use of wood waste as biochar for environmental remediation purposes. 

For lead in particular, scientists recently found that treating biochar with sodium hydroxide, which makes the biochar more alkaline (i.e., less acidic), improves biochar’s ability to adsorb lead. Sodium hydroxide treatment therefore represents a low-cost way to improve the ability of biochar to adsorb lead. 

• Biochar composite boards can remove 100 percent of mercury at 2 parts per million from water in 48 hours. 

• Biochar made from loblolly pine residues that have been exposed to the environment for up to 6 months can effectively adsorb lead from fresh water. 

• Treating biochar with sodium hydroxide improves its ability to adsorb lead from contaminated water.