The GACS+ Instrument Kit: Biochar Testing on a Budget

By Don Harfield (President & CEO, CharTerra)

The generally accepted and adopted standard for the determination of internal surface area and internal pore size is gas adsorption which is based on the Brunauer-Emmett-Teller theory, otherwise known as BET analysis. This is typically performed by a commercial or research laboratory, requires careful sample preparation, and is both costly and time consuming as you must wait several days or weeks for the results.

Hugh McLaughlin has developed a simple alternative method to sending biochar samples to a BET lab for analysis.

Hugh received his Doctor of Philosophy (PhD) in Chemical Engineering from Rensselaer Polytechnic Institute in 1988 and is a recognized expert in biochar, pyrolysis, activated carbon production, and characterization. He is based in Groton, Massachusetts and is the CTO of Trinity Biocarbon in Cairo, Egypt.

Hugh developed the GACS+ (Gravimetric Adsorption Capacity Scan) Instrument as an economical system that will determine the adsorption properties of biochars and activated carbons onsite and for a fraction of the cost of sending samples away for analysis. It also provides automated test results for moisture, ash, and volatiles content.

GACS+ Instrument for quickly determining biochar properties

How does the GACS Instrument Work?

Adsorption Capacity, as measured by GACS, is performed on pure biochar after it is made and before being blended or used for any application. If the biochar is wet, it can be dried and/or the GACS procedure will remove any residual moisture from the sample.

The GACS+ instrument kit consists of an analytical balance that is modified to measure the weight of a small sample of biochar or activated carbon as the adsorption capacity is “scanned” from high (300C) to low (100C) temperature. In addition to the adsorption capacity, additional information, such as moisture content and relative volatile levels, are collected during the period of time when the sample is heated to the higher starting temperature of the scan.

Hugh claims that the GACS method is a proven, cost effective and time efficient method of characterizing the adsorption properties of microporous carbon materials such as biochar and activated carbons. He claims the results are more accurate than the conventional BET analyses, especially considering the heterogenous nature of the carbon samples.

In general, a GACS instrument cannot be absolutely calibrated against other instruments due to the accuracy of the temperature measurement and calibration, which may be off several degrees between identical thermocouples and may drift over time due to aging of the thermocouple. In addition, repeatability of consecutive runs is +/- 2 to 5 percent, so avoid “squeezing the data”.

GACS+ Instrument Availability

Hugh has a limited number of GACS+ Instrument Kits for sale which are provided with all the components pre-assembled and pre-programmed with Win Wedge software onto a laptop. The current cost is $ 5,000 USD within the US and, if offshore, the additional costs for shipping and import fees. The system includes a heated chamber with the sample holder inside, temperature controller, analytical balance, and a vibration-isolating stand. The nitrogen (or propane or R134a) vapour supply and flow control system is included however the pressure containers would need to be sourced separately. Hugh will provide technical advice and coaching through several sessions over the telephone as well as the necessary standards to follow to validate the lab results.

Hugh expects the purchaser to be a nerdish type of science technologist to build and operate this system. For that individual, the results should be very rewarding! He recommends the instruments and GACS methods for university researchers and production facilities that need to routine confirm the properties of biochars.

For more information, or to purchase a GACS+ Instrument Kit, contact Hugh directly at hsmclaughlin@verizon.net.

Don Harfield is President and CEO of CharTerra, a biochar consulting firm serving Western Canada. Don is a seasoned executive, professional engineer, project manager, production operations & facilities optimizer, and researcher with over 40 years experience in waste management, oil & gas production, and the pulp & paper industry. He was also the technical lead for the Alberta Biochar Initiative. He applies his comprehensive knowledge to help clients navigate their way to success.