Biochar Production System

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
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
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.

Mechanical Specifications
This section will be completed upon proper specification of materials.

Electrical Specifications
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 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.

Thermal Specifications
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
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.

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








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.

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.

Test Results
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
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.

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 0-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.

Biochar Reactor Quality Tests
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.