Biochar Production System

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2017 University of Idaho Capstone Senior Project
Final Design Render
Sponsors University of Idaho, College of Engineering
Team Name Biochar
Duration Fall 2017 - Spring 2018
Company Liason None; N/A
Faculty Advisor Dr. Dev Shrestha
Team Members Jake Hall, Adam O'Keefe, Rachel Rosasco, Will Seegmiller, Joe Stanley
Questions or Comments?
Brief Purpose Video Biochar Overview

In the 150 miles that surround the area of the Palouse nearly 2 million tons of waste biomass are accumulated each year. This waste is nearly valueless, taking up valuable space at lumber mills that could be used instead for equipment or inventory. Currently lumber mills try to sell this waste biomass at up to 25 dollars a ton, and in many cases are even having to pay someone to ship it away. The idea is to take this low value waste and turn it into a high value product, biochar, which can be sold for $2000/ton. Along with the problem that the lumber mills are having, the farming industry is struggling with topsoil degradation. Currently the topsoil is becoming less and less nutritious which is creating problems for an industry trying to feed a growing population. As a consequence farmers are needing to use more fertilizer to grow the same number of crops. This causes both economic and environmental problems, as this is a cost intensive solution and reduces the amount of phosphorus available, a key ingredient in fertilizer. All these problems create a business environment with a unique opportunity to allow our product to kick start a brand-new market here in the U.S.

Development and Project Goals[edit]

Our team’s mission is to develop and prototype a model of a scalable, practical retrofit for modern, industrial boilers that will produce biochar for sale and heat energy. This design must account for multiple variables and allow control of input and output flow rates amongst other factors. ​


In an attempt to take advantage of biochar’s potential and start a new market in the U.S. the team is designing an attachment that will go on a pre-existing boiler and produce biochar at a continuous rate. This system uses exhaust heat from the boiler system to pyrolysize the waste biomass to produce biochar. This means that it will not take any resources the lumber mill already has. It is recycling various aspects of their operation to provide an economically viable solution to the biomass waste that is accumulation. This device will move lumber mills towards a minimal waste operation.

To summarize, our goals are:

  • Design a biochar reactor.
    • The reactor should function as an accessory for existing boilers and furnaces.
    • The reactor should use as little energy as possible.
    • The reactor should be easy to retrofit and as non-invasive as possible.
    • The reactor should produce biochar at a continuous rate, not through a batch process.
  • Build a prototype.
    • The prototype should be portable.
    • The prototype should be fully functional.

Design Specifications[edit]

The needs and constraints designated by the client for the final design include: continuous process​, easily integrated to a boiler system​, scalable industrial design, energy efficient design, dynamic control system​, and function as heat exchanger.

This design should be unique and different from other available biochar reactors in the sense that it should operate using available heated gasses exhausted from a preexisting boiler system. In a sense, this system should serve as an attachment that can be added to existing boilers so that they are able to incur additional value from waste biomass.

Mechanical Specifications[edit]

Our team has decided to work with incorporating a 1/2 Horsepower 3-Phase motor rated for 3600RPM as the primary auger energy source. To allow for ample cook times for the biochar, the motor will be geared down with a system of pulleys and belts. The gear reduction ratio is just over 3000:1. Not only will this supply the necessary speed reduction, but it also greatly increases the amount of torque delivered to the auger system, allowing for effective transportation of the biomass through the reactor.

In addition to the drive motor, the design makes use of three existing fan and motor assemblies. Two of the fans are small 230V squirrel-cage fans, and the third is a much larger 120V 1/2 Horsepower squirrel-cage fan. The three motors are to be speed controlled by use of the control systems described below.

The design makes use of a built-in "boiler" which, quite simply, is a 55-gallon metal barrel with a large 55kBTU rated propane burner mounted in the bottom. The boiler requires a large hole in the top for heated gasses to escape and enter the auger-based reactor.

The auger-based reactor system uses an inner and outer chamber system; the inner chamber contains the auger and the biochar which is being cooked, while the outer chamber contains the heated gasses exhausted from the "boiler". The inner chamber has many appendages not unlike heat-sinks built onto its exterior. This creates additional air-turbulence inside the outer chamber, and thus allows for greater heat transfer to the inner chamber, and by extension, the biomass. The inner chamber is made of a stainless-steel sheet rolled into a tube with many 1-inch "heat sinks" of 1-inch angle-iron welded onto its outer surface.

The biochar-collection bin is specified to be created from an old 2-drawer filing cabinet. A large hole cut in the top of the bin allows for cooked biochar to enter the bin, and the existing drawer is used to contain it and collect the material for easy extraction. The drawer and cabinet is intended to be sealed by use of furnace-type gasket material and heated gasses are to be extracted from the bin by use of one of the blower-fans previously described.

Electrical Specifications[edit]

Block Diagram of Electrical System and Control

Project designs were requested to use an existing Programmable Logic Controller (PLC) produced by AutomationDirect; the Productivity2000. The PLC was a modular system with room for a power supply, main controller and communication board, and 4 I/O modules.

The PLC makes use of 4 modules; a toggle-switch based digital input, a relay-based digital output, an analog input reading voltage, and a Thermocouple input module. In addition to the modular I/O, a touchscreen control panel is used for user interface and will control motor operation and display temperature and oxygen levels. The PLC is also responsible for basic operations including the system-startup procedure, and it operates in one of two modes, Demo-Mode or Active-Mode. The Demo-Mode only allows operation of the motors and does not use the startup procedure to ignite the fuel supply, the active mode allows control of the fuels supply and automatically engages the startup procedure.

The project requires the control of 3 motors by use of GS1 Variable Frequency Drives (VFD's) also produced by AutomationDirect. These VFD's use industry standard Modbus protocol over a 2-wire RS-485 connection as their primary control communication. This connection supports addressable operations, thus allowing all three VFD's to communicate over the same connection.

In addition to the three VFD-controlled motors, it is also necessary to control an additional 1/2 horsepower single-phase motor whose rated current draw far exceeds the ratings for the VFDs used for the other motor controls. This motor still requires speed control, however, and thus a system of Pulse-Width-Modulation (PWM) is used to control the motor. A electro-mechanical system using relays operating on a 1-second fixed period controlled by the PLC is used to control and energize the motor. This system will work due to the motor's enormous natural turn-on or turn-off time. It takes the specified motor 20 seconds or longer to turn on and rev to full speed, and it takes even longer to turn off and stop. This means that a PWM system with a 1-second period works effectively for the system.

The electrical system is also specified to ignite the fuel supply of propane. To do this, the PLC uses one of the relay contacts to energize a single-phase 120-3000V transformer designed for neon-signs to create an arc and ignite the propane burner. The PLC uses another relay contact to energize a normally closed solenoid valve and open the propane line to allow fuel to reach the burner. This process is monitored by the temperature probes and the PLC so that if the temperature does not rise (the fuel doesn't ignite) the system goes into a lockout-state where it shuts off the fuel supply and vents dangerous gasses.

This project also makes use of safety precautions such as emergency stop buttons. These are connected directly to a electro-mechanical lockout-relay that, if activated, removes all power from the entire system which will force valves closed and all systems to stop.

Thermal Specifications[edit]

From speaking with our graduate student advisor, Brian Hanson, and various sources online who describe the production of biochar and the requirements of an effective system, our team came to understand the thermal requirements. Temperature is a major component of the resulting material output of a pyrolysis system. Cooked under higher temperatures, biomass tends to release higher amounts of volatile gas and tar-like bio-oils. Alternatively, when cooked under lower temperatures (those around 450°C), pyrolysis tends to lend a higher biochar yield, and a smaller amount of gas and oil.

Due to this understanding of the thermal constraints, our team has conducted testing to determine the quality of biochar cooked in the range of 450°C.

Project Learning[edit]


Biochar dates back 2,000 years to a civilization in a remote region of the Amazon Basin where regions of dark, highly fertile soil has been discovered.​ It is theorized that the ancient Amazonians used a process known as “slash and char”, where the biomass (plant material) were cut, ignited and buried to smolder.​ This process allowed the Amazonians to support a diverse agriculture and explains how their population grew to immense numbers.

Life with Biochar

Biochar is rich in fixed carbon and has an enhanced surface area caused by micro and macro pores that easily absorbed and maintain moisture and nutrients. When it is integrated into soil it works to bring soils from both ends of the spectrum, sandy and clay soils, to a more nutrient rich middle.

Biochar is a very powerful soil enhancer, which makes the soil more fertile, boosts food security, and reduces the need for some chemical fertilizers. Given all of biochar’s qualities it is capable of aiding farmers in meeting the demand of a growing population and reducing the need for more fertilization.

In addition to learning valuable information about biochar and its properties, our team also learned a variety of information about its production and various techniques to produce it. As it was found, biochar is commonly produced by backyard gardeners and soil enthusiasts alike. These enthusiasts and gardeners often produce biochar in small, batch-process cooks that result in high ash content and inefficient cooking.

Over the course of project learning, it was discovered that there are also some companies in Europe that are working to produce medium-scale, standalone biochar reactors. These reactors produce their own heat energy and biochar exclusively. These systems are designed for small business and production, they don't appear to be very versatile or able to be scaled up.

Concept Development[edit]

Biochar Design Model 1
"Through-Boiler" Design
Biochar Design Model 2
"Inclined Auger" Design
Final Design Render Back
Final Design Render Front

Early concept design for a biochar reactor began with research into the world of existing designs. Various models and prototypes are available in a variety of online publications. To find ideas, inspiration and known working designs, our team spent several weeks researching biochar reactors online. To further our understanding of our goal and mission, our team visited the University of Idaho Steam Plant and were given a tour of the plant's wood-fired boiler and feed-stock supply system.

During early design stages, our team researched and found information describing a variety of backyard reactors made from countless recycled objects. Of these designs, several in-ground "planted" reactors were found. These systems simply burned the input biomass as feed-stock in an ultra-low oxygen environment to produce small quantities of biochar underneath a layer of ash and charcoal. These systems were designed primarily for homeowners and gardeners who wished to produce a small amount of biochar.

Other small-scale designs found included a cone-shaped reactor that used heated airflow to prevent oxygen from entering a burn-container. This design, lovingly called "The Cone" by our team, allowed the biomass feed-stock to burn and smolder on top of a layer of biochar covered in ash. This system, too, used ash and low oxygen to produce biochar directly underneath an open flame. Although both systems were described as highly effective and extremely simple to build, neither provided any room for development to allow for continuous flow.

Later, after reviewing online descriptions of various biochar reactors, our team visited the University of Idaho Steam Plant and got an up-close look at what makes the boilers so effective. The tour gave our team a first-hand view of different methods of biomass transportation including augers, belts, and elevators. During the tour, and shortly afterwards, our team began brainstorming a variety of ideas using these various conveyors to create a continuous-flow biochar reactor. The tour also opened up a variety of questions about the method of heating the reactor.

One of the very first models developed was that of the "Through-Boiler" design. Team members pitched the idea of placing a sealed auger-based conveyor directly through the heart of an existing boiler. This method would provide powerful, direct heating of the biomass, and it would allow for very short cook times. However, from this design, a variety of questions and problems were discussed. The first of many was how practical it might be to drill, or cut, holes in the sides of an existing boiler or firebox; not to mention how practical might it be to seal these new holes. Another question arose from the very method of fast cook-times. The amount of biochar in relation to volatile-gas and bio-oils is often related to the temperature of the cooking environment. Higher temperatures often mean less biochar, more gas and oil. Ultimately, this idea was set aside for more practical designs.

Following the first design, an external version of the "Through-Boiler" design was brainstormed. Known as the "Surface-Reactor" (not pictured), this design solved the problem of drilling holes in the sides of an existing firebox. This design also resolved the issue of extreme temperatures from direct heat from the fire. This solution, however, also spelled ruin for the design. After consulting Scott Smith, the University Steam Plant's resident expert, it was found that skin temperatures of the boiler are only approximately 450 degrees Fahrenheit. This temperature was lower than desired for production of biochar, rendering the design useless.

Final Design Side-Cutaway

Following these designs, the first practical model was developed. The "Inclined Auger" system relied on exhaust gasses from an existing boiler or firebox to produce the necessary temperatures to cook biomasses into biochar. This method solved several problems with very few realized concerns. By using exhaust gas, the Inclined Auger would be able to control the temperature of the reactor by using an exhaust valve and a system of blowers. The system also required very little interference with the existing boiler or furnace. This proved to allow the reactor a more modular and transportable design, increasing value and ease of use. This system used an inner- and outer-shell design, transporting biomass through the inner chamber as it was cooked into the resulting components. The outer-shell conveyed the heated gasses, allowing them to directly heat the pipe that contained the biomass and driving auger.

This first practical model was widely accepted by team members as it showed great promise. Ultimately, however, the design was found large and cumbersome for prototype testing and development; with this, the inclined boiler saw great revision.

To allow for a more practical prototype development, our team decided to remove the inclined nature of the first practical design. Instead using a horizontal path of motion, our final design retained all of the valuable features from the Inclined Auger model with more practical functionality. With this new-found idea, our team was able to craft a system around existing and available parts including a large shop-cart serving as the base and a 55-gallon barrel that would act as the boiler, and a provider of heat for the reactor prototype.

In the course of one evening, our team was able to hash out the basic structure of the design and take a considerable number of concerns into account. This design proved to be very practical on paper as it allows our team a wide array of configuration methods. A variety of ways to incorporate parts whose placement was uncertain was gained by use of the horizontal design with the shop-cart.

Seeing the potential for this design, our team moved forward, creating 3-D renders of the prototype to further visualize the magnitude and impact of the machine.

Project Timeline[edit]

Team Project Timeline

Competitions, Demonstrations, and Awards[edit]

Our team has spent great effort in developing our concept and designing our prototype. We firmly believe that this design yields great potential beyond the academic environment as a full-scale system, and as such we have participated in several business and design pitch competitions. We have won some of the competitions we've entered and with the help of three University of Idaho College of Business students (Charles Dolar, Audrey Wootton-Franusich, and Devin Kohles) we were able to demonstrate our idea to business professionals from around the state.

University of Idaho Pitch Competition[edit]


Our team competed in the University of Idaho's 2017 Idaho Pitch competition. Self proclaimed as a program that "gives innovators and entrepreneurs from across the university the opportunity to practice their presentation skills, build confidence, and learn how to work a reception - while presenting their ideas to a group of business and professional judges." Even with little business background or preparation time, our team was able to excel to the third-place position, winning $750.00 that we are using to further develop our design. Our success with Idaho Pitch ignited interest in our team from Idaho Entrepreneur Director and Instructor, George Tanner, who has encouraged and supported our team in continuing to promote our design in Boise and Spokane at competitions during the spring of 2018.

Boise Pitch Competition[edit]


Our team entered and was accepted for a pitch competition in Boise similar to that held by the University of Idaho. The competition took place on the 17th and 18th of March. Our team worked closely with three Business students to further develop a business model and other elements necessary for the competition. The experience was very valuable to the participating team members, and our team won $1,000 at the competition.

University of Idaho Engineering Expo 2018[edit]


Our team will be demonstrating our completed prototype at the 2018 University of Idaho Engineering Expo. We have worked to ensure that our system can work in a "demo-mode" where we can demonstrate the moving parts without actually having to ignite the boiler. Thus we will be able to demonstrate the flow of our system without having to actually start it.

Test Results[edit]

Low-quality biochar can be just as harmful as its high-quality counterpart is helpful. A great many backyard gardeners and growers have learned how detrimental poor biochar can be to the soil and garden environment. Poor biochar can be acrid, thus adding unneeded acidity to the garden soil. Poor biochar also isn't very porous, and thus can't retain nutrients or water well.

Preliminary Biochar "Pipe" Quality Tests[edit]

Test Pyrolysis Results

As an initial benchmark our team decided that it would be valuable to run some initial tests on biochar production. With some assistance from graduate student Brian Hanson, our team was able to conduct tests on biochar of various materials at different temperatures. The results have helped to guide our team towards some of the thermal requirements before mentioned.

Test Pyrolysis Results

To complete our tests, our team used a testing apparatus consisting of a metal pipe caped and sealed at each end. The metal pipe provided a zero-oxygen environment since after being filled with biomass, the pipe was filled with the inert gas nitrogen and then sealed. This apparatus was then placed inside an oven and "cooked" at various temperatures for varying lengths of time. We cooked a variety of materials to see the differences between the resulting biochar material.

Our team cooked such materials as wood chips, coffee husks, and wood fiber. This was important to our development since although our project primarily deals with wood chips, the other materials could prove to be future biomass sources.

Test Oven
Samples Before Cook
Oven Interior
Final Biochar Product

Biochar Reactor Quality Tests[edit]

This section will be completed upon completion of construction. When the biochar reactor is functional, then it will be used to test various configurations and determine biochar quality.

Team Members[edit]

Photo Biography Discipline
Jake Hall
From Coeur d'Alene, Idaho; Jake Hall formed a passion for mechanical engineering growing up working in the automotive industry. Through various job endeavors, mechanical systems and problem solving have always been a fascination of his. This led to his pursuit in attaining an engineering degree at the University of Idaho. ME
Adam O'Keefe
From Boise, Idaho. Adam O'Keeffe was destined for attending the University of Idaho because his whole family has gone to the University of Idaho. His enjoyment of the outdoors and living an active lifestyle dictates his daily life. His fondness for problem solving lead him to the Biological Engineering field. BE
Rachel Rosasco
Rachel was raised on her family's ranch in Jamestown, California where she developed a passion for the outdoors. She chose to attend the University of Idaho and major in Biological & Agricultural Engineering where she could apply an interest in math and science to solving agricultural and environmental problems. BE
Will Seegmiller
Born in Moscow, Idaho, Will Seegmiller was raised in Troy, Idaho and developed a great interest in Mechanical Engineering. He aimed to solve practical problems that have a potential to advance technology and improve the human condition. ME
Joe Stanley
From Weippe, Idaho; Joe Stanley grew up around 4-H youth programs. He worked on a variety of electrical projects that he applied to these youth programs, and his fascination with electrical engineering was formed. EE
Biochar Production System Team and Business Student Team

Project Construction Photos[edit]

Additional Team Documents[edit]

Project Schedule

To-Do Tasks

Meeting Minutes