Investigating the elasticity of biochar: manure handling, compost feedstock, soil amendment and carbon storage.

Progress report for OW19-342

Project Type: Professional + Producer
Funds awarded in 2019: $49,988.00
Projected End Date: 09/30/2022
Host Institution Award ID: G262-19-W7502
Grant Recipient: WSU
Region: Western
State: Washington
Principal Investigator:
Dr. Nathan Stacey
Washington State University
Alana Siegner
University of California, Berkeley
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Project Information


Investigating the elasticity of biochar: manure handling, compost feedstock, soil amendment and carbon storage.

Our collaborative team of beef producers, commercial composters, diversified vegetable farmers, and research and extension professionals will assess the impacts of biochar on manure handling, composting, and soil quality in western Washington. Biochar feedstocks will be sourced locally, from both coniferous and deciduous woody biomass.  Two biochar products from two different locally sourced feedstocks will be added to cattle bedding at Midnight’s Farm in a controlled, replicated experiment that will assess the influence of biochar on nutrient content of the bedding feedstock. The bedding- biochar blends will then be co-composted with other on-farm feedstocks at Midnight’s Farm, which is a Department of Ecology farm-exempt facility. The finished compost will be tested for agronomic mineral concentrations, and along with compost-only, biochar-only,  and no amendment control, the co-composted products will be amended to research plots on two participating farms (Lopez Harvest and Helsing Junction), and cropped to cabbage. Following the growing season, crop yield will be measured, and soils from research plots will be tested for nutrient content and carbon dynamics. Participating farms will conduct education and outreach activities related to biochar application in the form of on-farm demonstrations, workshops, outreach to other western state extension professionals, and field trips from local schools. This collaboration is especially well suited to take on this project as it combines two extension professionals from WSU, a U.C. Berkeley graduate student with farm to school educational expertise, one biochar consultant, and five producers. The combined expertise and enthusiasm of this group lends great momentum to the research question at hand: can biochar be a multi-use farm product that improves farm based co-composted products and vegetable production, and promotes soil C sequestration?

Project Objectives:

The objectives of this Professional + Producer collaboration are to answer the following questions: what are the physicochemical effects on livestock bedding when different biochars are incorporated, and then composted? Subsequently, what is the effect of biochar co-compost on promoting plant growth, soil health, and fertility? Specifically, our objectives include:

  1. Evaluate two different biochars, one sourced from coniferous woody biomass and the other from deciduous woody biomass, as livestock bedding additives and test whether biochar incorporation improves feedstock nutrient concentration (i.e., nitrogen).  Assess whether the different bedding feedstocks (i.e., 2 different biochar blends and a control) alter the physicochemical properties of finished composts (e.g., water content and nutrient concentration).
  2. Demonstrate, compare, and document effects of co-compost, compost, and biochar soil amendments related to:
    1. Crop yield in field application
    2. Soil health and fertility
  3. Evaluate biochar as a carbon storage farming practice.
  4. Educate other farmers in the region interested in producing and/or applying biochar to their farming systems on how to do so and what to expect (from the feedstocks used in this trial).
  5. Educate other researchers and cooperative extension specialists about biochar co-compost applications and how to communicate and advise interested farmers.

The long-term goal of this project is to improve soil and water quality while sequestering carbon in soils. Our objective is to evaluate the nutrient content of two biochar blended, cow bedding feedstocks, observe and document how the resulting composts differ, and then test the different co-compost as soil amendments.  We hypothesize that: 1) blending biochar into cow bedding will result in greater N retention, reducing the potential for environmental loss, 2) adding the biochar bedding blend to compost will increase nutrient content, thereby adding value to the compost product, and that 3) compost with biochar as a feedstock will lead to increased soil carbon, cation exchange capacity, and pH when applied to soil.




September 2019

Produce deciduous biochar.

October 2019

Apply biochars to cow bedding (40% by volume), incubate, and sample.  Repeat 2 additional times.

November 2019

Promote project at Washington Organic Recycling, or Tilth Alliance, conference.

January 2020

Co-compost biochar and bedding feedstocks in 3 vessels, sample and analyze compost.  Repeat 2 additional times.

February 2020

Seed cabbage transplants.

Sample soils at Helsing Junction and Lopez Harvest farms for pre-amendment analysis and soil C experiments.

April 2020

Amend soils at Helsing Junction and Lopez harvest farms.

September 2020

Collect soil for soil C incubations and experiments.

September/October 2020

Pre-harvest cabbage for yield analysis.  Collect soil samples for soil fertility evaluations.

November 2020

Initial biochar/bedding results presented at Washington Organic Recycling, or Tilth Alliance, conference.

February 2021

Education/Demonstration event at San Juan Agricultural Summit, hosted on Lopez Island by Midnight’s Farm and Lopez Harvest.

April 2021

On-farm workshop at Helsing Junction for off-Island farmers, research and extension personnel.

February 2022

Final results presented at Oregon Small Farms conference.


Click linked name(s) to expand/collapse or show everyone's info
  • Janet Aubin - Producer
  • Kai Hoffman-Krull - Technical Advisor (Educator)
  • Kai Hoffman-Krull - Technical Advisor (Educator)
  • Christine Langley - Producer
  • Arden Paige - Producer
  • Roger Short - Technical Advisor - Producer
  • Roger Short - Technical Advisor - Producer
  • Alana Siegner (Educator and Researcher)
  • Alana Siegner (Educator and Researcher)
  • Dr. Nathan Stacey (Educator and Researcher)
  • Dr. Nathan Stacey (Educator and Researcher)
  • Faith Van de Putte - Producer


Materials and methods:

Objective 1:

  • The coniferous biochar is made commercially as a byproduct from Douglas fir and pine forestry residuals, heated to 870 degrees C in a low oxygen environment and sieved to a particle size of 1 - 4 mm.  Deciduous biochar will be produced during the fall of 2019 with input from Forage, Shorts, and FinnRiver farms - all who have experience producing biochar.  To ensure that comparisons between biochars represent feedstock differences and not those of production, manufacturing conditions for the deciduous char will be matched to those of the coniferous char.
  • Currently, Midnight’s farm cows are bedded on ground wood debris where manure is incorporated. The two biochars will be integrated into the manure-handling process in a controlled, replicated (n=3) experiment. Biochar and wood debris bedding will be mixed in shallow containment vessels and manure will be collected weekly, homogenized, sampled for nutrient content and re-distributed at a known amount into each vessel during a 3-week incubation period. Following incubation, the feedstock blends will be tested for nutrients then composted (see below). To include 10% biochar (v/v) at the beginning of composting biochars will be incorporated into cow bedding at 40%; manure addition will dilute this by half and then additional composting feedstocks will dilute by half again.
  • The three feedstocks (two biochar/bedding blends and one bedding control) will be moved to the composting study to determine biochar effects on compost.  Bedding will be combined at a 50% (v/v) rate with other feedstocks in 1.7 cubic meter composting vessels and composted until maturity.  Compost from each vessel will be analyzed using standard compost evaluation (moisture content, total N, total C, and other plant macro- and micro-nutrients).  The process will be repeated 2 additional times and each of the three composts from three compost periods will be homogenized and stored until amended to soil.

Objective 2:

  • For the on-farm field experiments and prior to amendment, soils at each farm will be sampled to a depth of 15 cm and analyzed to identify obvious deficiencies or imbalances (e.g., pH); if necessary, soils will be amended accordingly (WSU researchers).
  • In a randomized complete block design with four replications, the three compost products, and each of the two biochars, as-is (6 treatments, including a control), will be amended to research plots (3m x 3m) at Helsing Junction (24) and Lopez Harvest farms (24) and then tilled to a depth of 15 cm.  To equalize the amount of C that is added across treatments, an application rate that is equal to 10 Mg C ha -1 will be used as the target rate which, will be calculated following compost analysis.
  • To evaluate treatment effects on crop yield, research plots at each farm will be cropped to cabbage and prior to harvest, biomass from two, 1 m length sections (~ 20 plants) will be collected, counted, and then weighed.  The average of the two measurements will be taken as yield (WSU researchers).
  • Prior to amendment and approximately one to two months prior to harvest, soils from both sites will be collected to a depth of 15 cm, incubated for 4 days and analyzed for CO2 concentration, a reliable estimate of soil microbial activity and physical availability of carbon compounds.  In addition, soils will also be analyzed for permanganate oxidizable carbon (POXC), a good indicator of C storage potential.  Both methods are included as soil health indicators in the NRCS draft technical note for 2018 (WSU researchers).
  • At the end of the growing season, to evaluate soil fertility, soils from all research plots will be collected and analyzed for pH, cation exchange capacity, total N, total C, and plant available N forms (ammonium and nitrate) (WSU researchers).

Objective 3:

  • The on-farm field trials are both replicated, designed experiments; the 6 treatments combined with the two soil C experiments (i.e., incubation and POXC) will help to elucidate how biochar affects existing C mechanics and thus, potential C sequestration.

Objective 4:

  • To promote the project, a brief presentation will be communicated to attendees at the Washington Organic Recycling, or Tilth Alliance, conference in the fall of 2019 and 2020.
  • In 2021, the San Juan Agricultural Summit will be used as the venue for educational outreach to local farmers, and others, interested in the use of biochar.  Preliminary results from the biochar/bedding experiment and the co-compost field trials should be available by this time.

Objective 5:

  • Building off the interest created at the San Juan Agricultural Summit, Helsing Junction farm in collaboration with Midnight’s and Lopez Harvest farms, will host an on-farm workshop late in the Spring of 2021 that will specifically target regional farmers, researchers and extension professionals.  By this time, most data will be analyzed (e.g., survey and soil evaluations) which will allow researchers to make appropriate recommendations for effective communication strategies and on-farm use.  Full results will be communicated at the Oregon Small Farms conference in February of 2022.
Research results and discussion:

Objective 1:

Owing to the vagaries of biochar production, we decided to utilize a local commercial biochar producer for our second biochar product instead of pyrolyzing our own biomass.  The first biochar product, purchased from Oregon Biochar Solutions in White City, OR, is made from Douglas fir and pine forestry residuals heated in a biomass boiler at 871 °C (1599.8 °F) and the second, purchased from Olympic Biochar, a local producer based in Port Townsend, WA, is made from clean construction and demolition debris (1/3) and hog fuel (2/3) which, is a blend of Douglas fir, hemlock, cedar, and alder but, is produced a 1100 °C (2012 °F). 

  • Table 1. lists some physical and chemical characteristics of the two biochar products.

Table 1.  Physical and chemical characteristics for the Olympic and Oregon biochar utilized in the on-farm research.

Biochar product Total C (%)* Total N (%) C/N Ash (%)

Surface area (ftlb-1)

Particle size range (in)

Olympic biochar 80.7 0.97 83.2 6.5 1.758 x 106 <0.019-0.315
Oregon biochar 88.0 0.78 112.8 3.7 2.226 x 106   0.039-0.157
*Total C, N and Ash are on a dry weight basis.

The Olympic and Oregon biochars were blended with the manure/bedding mix in each of two 150 gallon stock tanks at a rate of 160 and 102 lbs (26 and 46% (v/v)), respectively.  A third stock tank filled with manure/bedding mix alone acted as the control.   Following a three week incubation, the material from each treatment was randomly sampled and analyzed for the total amount of C and N, as well as concentrations of nitrate (NO3-) and ammonium (NH4+), and all were conducted on an as-is and dry weight basis.  This entire process was replicated three times. 

  • No significant differences were observed between treatments and in any of the tests evaluated.  During the feed stock experiment, we experienced unusually high precipitation and thus, the manure/bedding mix was saturated at the time of mixing.  The high water content and low temperatures may have hindered mineralization and thus, neither biochar product would have captured excess nutrient.  This is supported by the non-detects that were returned for both the inorganic forms of N.  Mean values for selected analytes are listed in Table 2.

Table 2.  Mean values for selected analytes following stock tank incubation of three different treatments.

Treatment Moisture (%) Total C (%)* Total N (%)
Olympic biochar mix 75.2 44.6 1.20
Oregon biochar mix 74.5 53 1.23
Control 74.7 36.7 1.1
*Total C and N are on dry weight basis.

Each of the materials from the stock tank incubation was then used as feedstock, along with additional manure/bedding mix, in a replicated composting experiment that evaluated similar chemical properties (i.e., total C and N, inorganic N). 

  • Neither the Olympic nor the Oregon biochar greatly affected the nutrient contents of the composted materials.  In fact, similar to the stock tank incubation, concentrations of inorganic N (NO3- and NH4+) were below detectable levels, likely a result of the high moisture content (data not shown).  Differences in C/N ratios between the treatments reflected the additional C in the form of biochar, and the increase in total and organic N (Control>Oregon biochar compost>Olympic biochar compost) is likely a result of dilution, i.e., the Olympic biochar was incorporated at the highest material rate and thus diluted the concentration of N (Figure 1b, 1c, and 1d).  When we blended the biochars with the manure/bedding mixes, we added the same amount of C (dry wt.) in the form of biochar, so it is surprising to see the observed differences in total C between the treatments (Figure 1a).  These differences could result from inconsistent sampling, or, it may be that the biochars differentially affected C mineralization.
This image communicates the differences in compost chemical properties.
Figure 1. Treatment means for percent C (a), C to N ratio (b), percent total N (c), and percent organic N (d) following four weeks of composting. In each panel (a), (b), (c), and (d), the small letters below the blue circles ("a", "ab" ,"b") indicate statistical significance. If a blue dot has the same letter, those two values are not considered statistically different (e.g., "a" and "ab" are the same, while "a" and "b" are different).

Objective 2:

For the field experiment, six different treatments, including a control, were amended to research plots at Helsing Junction (Rochester, WA) and Lopez Harvest (Lopez Island, WA) farms in a completely randomized design replicated four times.  Rates for each amendment are listed in Table 3.  At each site, 24 plots were randomly assigned to two 100 foot beds and irrigated overhead, and by drip, at Helsing Junction and Lopez Harvest, respectively.  Due to COVID-19, our original plans for a spring cabbage planting were altered.  Instead, we planted starts of "Green Magic" broccoli and harvested main and side shoots once they reached marketable weights during the fall of 2020.

Table 3.  Amendment rates for each of five materials used in the field experiment at Helsing Junction and Lopez Harvest farms.

Amendment material Mg Ha-1 (wet wt.) Lbs acre-1 (wet wt.)
Control compost 70 62,452.5
Olympic biochar compost 69 61560.4 
Oregon biochar compost 65.7 58616.2
Olympic biochar 38.8 34616.5
Oregon biochar 25 22,304.5


  • Unfortunately, broccoli plants at Helsing Junction were uniformly damaged by a slug infestation.  Even so, main shoots were collected as planned and mean values for the treatments, following amendment, are presented in Figure 2a.  Broccoli plants at Lopez Harvest favored well and main shoot weights did illustrate an increasing, though insignificant, trend following amendment (composted materials>biochar materials alone>control)(Figure 2b).  This trend likely reflects the additional plant available N added from the materials.  In comparisons between treatments, however, no significant differences were observed in main shoot, side shoot, or head number observations following amendment (Figure 2, a,b).


The graphs depict broccoli yield at two different farms.
Figure 2. Broccoli main shoot yield following amendment for Helsing Junction (a) and Lopez Harvest (b) farms.

From both sites and to a depth of six inches, soils were sampled at three times: before amendment, mid-season, and just before harvest.  Analysis at each time point and for the different analytes (soil fertility and C dynamics) are underway and will be completed mid-summer 2021.  Following harvest and to better understand how each of the 5 materials affected soil physical properties, we collected soil bulk density cores from the 24 plots at each site. 

  • Interestingly, the Oregon biochar, which was amended at the lowest rate (Table 3), was the only treatment that reduced soil bulk density in comparisons with a control (Figure 3 a,b).  The decrease in soil bulk density (~0.25 g cm3) was consistent at both sites (Figure 3 a,b).  The varying proportions of labile and pyrogenic C (biochar) in the different materials may have an affect on native soil C cycling, but at this moment it is unclear what these observed differences reflect. The POXC and 4-day incubation analysis should elucidate some of the underlying mechanisms that may be affecting C storage.
This graph depicts soil bulk densities at two farms.
Figure 3. Mean values for soil bulk density following amendment and one growing season at Helsing Junction (a) and Lopez Harvest (b) farms.

Objective 3:

Methods for objective 3 are slated to begin in the next month.

Objective 4:

  • Descriptions of the project, experimental design and to-date data were presented at the 2020 Tilth Alliance Conference, Challenging the Status Quo on November 9, 2020.
  • We plan to use the San Juan Ag Summit of 2022, instead of the 2021 offering, to describe the project in its entirety.
  • In addition, the project was presented at the Western Nutrient Management Conference on March 3rd, 2021.

Objective 5:

This will likely be moved to the fall of 2021, in the hopes that we can have an in-person gathering.

Participation Summary
5 Farmers participating in research

Educational & Outreach Activities

4 Webinars / talks / presentations
1 Other educational activities: Our collaborator, Midnight's Farm, sends out a regular marketing and farm information newsletter and the project was described therein.

Participation Summary:

5 Farmers
120 Ag professionals participated
Education/outreach description:

The project began in early December (2019) and Nathan Stacey and Doug Collins have been able to integrate descriptions of to-date, research work into two presentations.  Nathan Stacey described the project at the 2020 San Juan Island Agricultural Summit, where a portion of the research is located, and Doug Collins illustrated the research in one talk at the United States Composting Council annual conference and trade show.

As mentioned above, our collaborator, Midnight's Farm publishes a marketing and informational email newsletter where a detailed description of the project was written and communicated to recipients.

Clearly, plans for 2020 were vigorously disrupted.  Even so, Nathan Stacey presented the project in its entirety at the Tilth Alliance Conference on November 9, 2020 to an audience of agricultural professionals (industry), laypeople, farmers and university and agency personnel (~80 individuals).  A link to the presentation can be found here.  Additional data and work was presented at the Western Nutrient Management Conference on March 3rd, 2021, which includes research, extension, education and industry agricultural professionals.

It is our hope that by fall 2021, we'll be able to host an in-person soil carbon camp at our collaborator's property on Lopez Island. 

In addition, we plan to communicate the project and all results in the spring of 2022 in an appropriate venue.

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.