Bio char Kiln Fabrication and Operation

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2010: $3,893.00
Projected End Date: 12/31/2013
Region: North Central
State: Minnesota
Project Coordinator:

Annual Reports


Not commodity specific


  • Education and Training: on-farm/ranch research
  • Natural Resources/Environment: carbon sequestration, soil stabilization
  • Production Systems: organic agriculture
  • Soil Management: organic matter, composting

    Proposal summary:

    There is considerable interest in the use of bio char as a soil amendment both here in the US and abroad. Consensus is almost universal that bio char enhances soil fertility, water retention, and has potential as a carbon sink. The potential as a sink is actually tremendous, studies in the UK show increasing soil fertility up to 20 tons/acre of bio char. That is why I believe bio char has the best potential for organic farms devoted to small intensively cultivated plots such as vegetables, herbs, or fruits. And the most important part of this present scenario is the fact that there is little information on how a farmer could actually produce meaningful quantities of bio char with a repeatable process and at an economical cost. To address these problems, I would like to have three small metal kilns fabricated, based on a proven design. The design of the kilns is quite simple, metal rings four feet in diameter and two feet high. Two rings are stacked on top of each other and a round, flat lid is placed as a cap. Eight combination air inlets/chimneys are used to control the rate and location of the fire inside the kiln during charring. I have chosen to use 3 small kilns based on some of my own preliminary work. Smaller kilns are easier to fabricate and transport. A small kiln will complete the charring process in one day, cool down on the second day, and be ready to be loaded on the third. I estimate the production from each charring will be 250 lbs., so the monthly production would be 2.5 tons. This is enough to amend, at a rate of 20 tons/acre, a plot 75 ft by 75 ft. I would use downed wood and pruning trimmings from our land in Iowa and transport the char to a suitable site. I already have several ideas for using the char. I would like to try adding it to organic matter before composting, applying char in combination with legumes such as clover to pasture or fallow land, and using it as a sponge to absorb animal manures prior to application on fields.

    An alternate use for particular hardwoods such as oak or hickory could be the cooking charcoal market; there is increasing awareness and interest from consumers for such a more natural product.

    Project objectives from proposal:

    The objective of my project was to fabricate 3 kilns to produce charcoal for agricultural purposes and to evaluate their performance. During 2011 two different types of kilns were fabricated, used to generate bio char, and the char has been used under different conditions to evaluate its performance: direct application to soil, mixing char with composted manure and tilling the mixture into the soil, and incorporating the char into a compost heap. 2012 will be a year in which the work of producing char will continue and the char will be utilized in various ways to test its utility. I plan to continue incorporating a portion into compost piles, begin using char as a bedding material for composting worms, and applying a mixture of composted manure and char to soils. Work from 2011 is leading my inquiries. Last fall I mixed composted manure with char and tilled it into a plot of clay soil. This spring that section of garden was amazingly friable. Untreated soil was gooey and waterlogged, soil with only composted manure was also sticky, soil with char only was more friable and less gooey, but the mixture of char and manure was like potting soil, requiring only a twist of the wrist to loosen the surface. I've planted beans as a cover crop and I am beginning to document the experiment.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.