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

Final 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
Oregon 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:

  • Biochar was purchased from two commercial manufacturers, Oregon Biochar Solutions (White City, OR) (Bior) and Olympic Biochar Solutions (Port Orchard, WA) (Bioly), and produced from pine and Douglas fir forestry residuals at 1600 °F and from Douglas fir, hemlock, alder and pine hog fuel and construction debris at 2012 °F, respectively. 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.
  • Midnight’s farm cows are bedded on ground wood debris where manure is incorporated. The manure/bedding mix was collected from animal pens, mixed on a concrete pad, and scooped into each of three 150-gallon stock tanks.  Bioly and Bior were incorporated into each of two filled stock tanks at a rate of 40.79 lb C (dry), while the third filled stock tank, without biochar addition, was treated as the control.  The three tanks were placed in a dry covered storage area and allowed to rest - exposed to ambient air temperatures - for three weeks.  Then, three sub- samples from each of three stock tanks were collected, homogenized, and composited into an individual sample for each treatment.  Samples were sealed in plastic bags and frozen, and later analyzed for moisture, total C and N, and inorganic N, on a dry and as-is basis.  The remaining material was used as feedstock for the composting experiment and the entire process was repeated two additional times.
  • To evaluate the effects of biochar incorporation on the composting process, each of three stock tank materials (i.e., manure/bedding control, and two biochar blended manure/bedding mixes) was turned out onto a clean concrete pad, blended with 300 gallons of additional fresh manure/bedding material, and this new material (450 gallons in total) was homogenized and scooped into a 450-gallon, square plywood composting reactor.  The composting vessels were capped with 75 lb of wood chips and outfitted with temperature probes positioned midway between the top and bottom of the reactor (data not shown).  Reactors were placed in a dry covered area and the materials were composted for four weeks, sampled, and then analyzed for moisture, total C and N, and inorganic N on a dry and as-is basis.  This process was repeated an additional two times, and each of the three materials from all three repetitions were combined into separate piles and stored until use in the field experiment.

Objective 2:

  • Six treatments were arranged in a randomized complete block design, with four repetitions, across two, 100-foot, vegetable beds at two different farm sites.  The six treatments included: a control, Bior alone, Bioly alone, composted Bior (BiorC), composted Bioly (BiolyC) and a control compost (CC).

  • Treatments were applied, by hand, to 32 ft2 research plots to meet an application rate of 8921.79 lb C acre-1 (dry); amendment rates are listed in table 3.  Following application, amended plots were tilled to a depth of six inches, and evaluated for bulk density following one growing season.

  • Broccoli ‘green magic’ starts were grown from seed, in a greenhouse, for four weeks, and then transplanted into each of two beds, in two rows at 15 and 18 inch, in-row and between row spacing, respectively.  Broccoli plants were fertilized with a 12-0-0 feather meal product at 104 lbs N acre-1 and irrigated by drip irrigation.  Once main shoots reached a marketable size, they were collected, counted, and weighed.

    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 added across treatments, an application rate equal to 10 Mg C ha -1 was used based on compost analysis.
  • To evaluate treatment effects on crop yield, research plots at each farm were cropped to cabbage and prior to harvest, biomass from two, 1 m length sections (~ 20 plants) were collected, counted, and then weighed.  
  • Prior to amendment and approximately one to two months prior to harvest, soils from both sites were collected to a depth of 15 cm, incubated for 4 days and analyzed for CO2 concentration (MinC), a reliable estimate of soil microbial activity and physical availability of carbon compounds.  
  • At the end of the growing season, to evaluate soil fertility, soils from all research plots were collected and analyzed for pH, cation exchange capacity, total N, total C, and plant available N forms (ammonium and nitrate) (WSU researchers).

Objective 3:

  • Carbon content of finished composts and amended soil were evaluated.

Objective 4:

  • A presentation was given to attendees at the Tilth Alliance conference in the fall 2020.
  • Midnight’s farm, hosted on-farm workshops late in Fall 2021  and May 2022.  These events, marketed as "Midnight's Farm Climate School" specifically targeted regional farmers, researchers and extension professionals.  In addition to the in-person class, a hybrid on-line/in-person Climate Farm School course offered by co-PI Seigner shared the results of this project with participants. 

Objective 5:

  • In addition to agricultural professionals reached through the Farm Climate Schools, PI Stacey presented results from this project to the Western Center for Nutrient Management Annual Conference, March 2021
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 (1600 °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. Surprisingly, amendments did not affect soil active C (POXC) or mineralizeable C (MinC).  While Olympic Biochar alone tended to increase total C at both sites there was a slight, though not significant decrease in active C with Olympic Biochar relative to the control.  MinC was not significantly affected at either site, though the Olympic Biochar treatment tended to decrease active C relative to the control at the Helsing Junction site and increase MinC at the Lopez Harvest site.
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:

  • Carbon content in the finished compost was increased slightly with addition of compost (ControlCompost=32% C, Oregon Biochar Compost = 32.5% C, Olymbic Biochar Compost = 32.2% C.
  • Following application of treatments to soils in the two replicated field trials we did observe a significant increase in total soil C (p<0.01). The effect was more pronounced at the Lopez Harvest site.  There was not a clear indication that the biochar-amended compost or the biochar alone treatments resulted in more soil C.  The Olympic Biochar treatment alone and the Oregon Biochar Compost treatments both resulted in the largest soil C content across both sites.
Participation Summary
5 Producers participating in research

Research Outcomes

Recommendations for sustainable agricultural production and future research:

Compost experiment

The C and N content for the three composted materials was largely in line with expectations (Figure 1).  C/N ratios for biochar amended materials (BiolyC and BiorC) were significantly greater than the control, reflecting the additional C in the form of biochar (Figure 1b), and total and organic N concentrations illustrated small, but significant differences between treatments (i.e., Control > BiorC > BiolyC) (Figure 1c,d).  Given the low nutrient content of the biochars, the differences in total and organic N content likely reflect nutrient dilution, caused by the additional biochar material which was amended at different volumes (e.g., 15 and 9% (v/v), Bior and Bioly, respectively) to meet an equal amount of dry C.  This is further supported, in part, by the levels of NH4-N and NO3-N which were below detectable limits and thus, had very little impact on total N concentrations. 

Similar to the stock tank experiment, moisture levels were consistently high in all materials (75%) and no treatment significantly increased or decreased moisture content (data not shown).

Field experiment

There were no clear trends in soil bulk density values following amendment.  In comparisons with the control, only the Bior and BiolyC treatments significantly decreased soil bulk density (Figure 2).  Other researchers have observed linear relationships between soil bulk density and amendment rate (i.e., soil bulk density decreases as amendment rate increases), but in our study we observed nearly the opposite.  The CC treatment, amended at the highest material rate, had no effect on soil bulk density when compared to the control, while the Bior treatment, amended at the lowest material rate, had the greatest effect on soil bulk density.  The amount of labile C in each treatment may have something to do with this observation, but the inconsistent results, including bulk density values for BiolyC and BiorC treatments, make clear

interpretation difficult.

Following amendment and one growing season mean broccoli yields ranged from 6672 to 9079 lb acre-1.  In comparisons with the control, however, no significant differences in yield were observed between treatments (Figure 3).  This is likely a result of the high C/N ratios in the materials (Figure 1b).  Even so, as the C/N of the material decreased (composted materials < biochars), yields increased (composted materials > biochars).  This effect may have been more pronounced if we had not included a supplement N application which could have masked different N mineralization rates between treatments.  Additional plant nutrients supplied by the  compost and co-composted biochar amendments may have also contributed to the trend in broccoli yields.

At the rates utilized in this study, and when blended with manure/bedding mixes and composted, these two biochars had little effect on nutrient capture, and thus, no effect on broccoli yield.  Amending soils with biochar and co-composted biochar materials, however, did reduce bulk density, but the physicochemical properties of the material likely had an impact on the magnitude of that effect.  As many other researchers have observed, for biochar to be an effective environmental and farm tool, users must take into consideration, the physicochemical properties, application rate, and intended use of the biochar material.

1 Grant received that built upon this project
5 New working collaborations

Education and Outreach

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 participated
120 Ag professionals participated
Education and outreach methods and analyses:

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.

In fall 2021 and spring 2022 Midnight's Farm hosted an in-person soil carbon camp. The research supported by this grant was highlighted during both events. 

Education and outreach results:

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.  There were approximately 80 attendees. Based on evaluations from the workshop, 90% of attendees found the topic relevant and interesting and 90% indicated their knowledge of the topic greatly increased. 80% planned to make changes in their practices based on what they learned.
  • 10 people attended the Midnight's Farm Climate Farm School course in Fall 2021 and another 8 attended the course in May 2022. PI Stacey presented about the biochar co-compost research as part of his soil health workshop during both in-person events.
  • 65 people have completed the Climate Farm School course (PI Seigner) since Sept. 2021 and seen slides referencing the Midnight's Western SARE research project 
  • 100 people attended a webinar in January 2022 about the Climate Farm School program and heard about the research project as an example of on-farm climate focused research
  • Everyone who takes the Climate Farm School makes an action plan mapping out how they plan to change and evolve professionally to contribute positively to climate-resilient food system building 
  • Example of a participant testimonial that referenced the soil health session: "I feel like this is a great intro class to everything climate and food systems. If someone wanted to do a deeper dive I think there were enough resources/content provided to start ones own journey into that landscape. Soil health seems to be the most important bit of everything we learned. I wonder if doing some more with soil would be beneficial. The hands on testing we did with Nate [PI Stacey]was awesome, it's hard to understand soil science sometimes - so taking big ideas and doing fun experiments really solidifies the knowledge and enriches the experience."

Objective 5:

  • In addition to the agricultural professionals reached through the Climate Farm School, the project was presented at the Western Nutrient Management Conference on March 3rd, 2021. The primary target audience of this event are agricultural professionals.  The proceedings from this conference are included in this report.
64 Farmers intend/plan to change their practice(s)
1 Farmers changed or adopted a practice

Education and Outreach Outcomes

Recommendations for education and outreach:

Interest in use of biochar in soil, manure management, and as a composting feedstock is high. At the rates utilized in this study, and when blended with manure/bedding mixes and composted, the two biochars evaluated had little effect on nutrient capture, and thus, no effect on broccoli yield. Concentration of biochar for manure handling, compost feedstock, and soil amendment are likely important. It is possible that biochar at higher rates would have more significant impact on nutrient cycling and crop yield. Amending soils with biochar and co-composted biochar materials, however, did reduce bulk density. 

One area of interest in biochar is the ability to sequester carbon in soil.  The Olympic Biochar treatment alone (sourced from Douglas fir, hemlock, alder and pine hog fuel and construction debris and pyrolized at 2004 °F) resulted in the highest concentration of soil carbon at both sites. This material with, with a higher pyrolization temperature, may be more stable in the soil and better for sequestering carbon in the soil. 

Biochar can be made from many different types of organic materials. When choosing biochar as a soil or compost amendment one should have clear goals for its use and find the material that fits those goals.

65 Producers reported gaining knowledge, attitude, skills and/or awareness as a result of the project

Information Products

    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.