[USCC] Using wood ash in composting

[Chaney, Rufus]

Dear Ken Powell et al.:

 

Several others have given you good responses to your questions about
using wood ash in composting. A few other thoughts come to mind.

 

Because wood wastes being burned can include some CCA wood by mistake or
chance, wood ash may be quite rich in As. If CCA contains 3000 ppm As
(ash than perhaps 30,000 ppm), and you had 1% CCA wood wastes in the
burned bass, the ash would contain 300 ppm. Most compost is 5-10 ppm As,
so a little ash would add more As than the rest of the compost. This
would be very important in FL where they have required
remediation/replacement of soils with as little as 2 ppm As!!! And I
have talked with composting firms who used wood wastes for power
generation and had to put the ash in a landfill because of As due to the
small amount of CCA waste wood that is essentially impossible to detect
in large lots of wood wastes.

 

Except for the As question from CCA wood entering the burn or composting
operation, wood ash would be a valuable ingredient in an improved
compost. The alkalinity would seldom be important although a higher pH
during composting can cause some volatile loss of ammonia that would not
occur in an acidic composting heap. But most compost systems are neutral
pH and do loose ammonia during processing.

 

Regards,

 

Rufus Chaney

USDA-ARS

Beltsville, MD

 

Rufus L. Chaney, Ph.D.

USDA-Agricultural Research Service

Environmental Management & By-Product Utilization Lab

Bldg. 007, Room 013, BARC-West

Beltsville, MD  20705-2350

Phone: 301-504-8324

Fax: 301-504-5048