Life cycle analysis of different biochar production processes for simultaneous waste management and carbon capture credits

Conference Dates

June 5 – 10, 2022


Biomass pyrolysis has been extensively investigated to produce biooils, gaseous products and biochar and a number of successful commercial production facilities have been implemented. Gaseous products are mainly utilized for process energy recovery, whereas biooils have found broad applications that vary from food additives to fuels. On the other hand, biochar has attracted a growing interest in recent years as a valuable soil amendment, a precursor for high quality adsorbent materials, as a catalyst, as well as an efficient medium for carbon sequestration. Therefore, biomass pyrolysis can convert waste materials that decompose and generate greenhouse gases into a stable carbon that can offer intrinsic soil amendment properties while sequestering carbon in the soil for hundreds of years, thus representing a net carbon sink. Large scale biomass pyrolysis processes are traditionally based on fluidized bed technologies, rotary kilns, cyclonic contactors, auger or other mechanically mixed reactors. However, all these technologies require addition of external energy and feedstock pre-processing steps. An emerging alternative to produce large quantities of biochar is based on air-curtain carbonators. This technology consists of a combustion process which can handle very large quantities of raw unprocessed biomass materials. The feedstock is partially combusted to generate the process energy while generating quantities of unconverted carbon in the form of biochar and controlling the gaseous emissions by secondary combustion through an air curtain. All the biochar technologies have different impacts on the carbon balance between feedstock, emissions, and products. In addition, depending on the operating conditions and, particularly, the process temperature, the stability of the carbon in the products varies considerably. Consequently, Life Cycle Analysis (LCA) is the essential tool to evaluate the carbon management balance between the waste feedstock and the products, and, consequently, to evaluate the potential net carbon sequestration potential of the biochar. Carbon removal markets and corporate decarbonization have been popular topics in recent months. A growing number of companies are qualifying to sell biochar CO2 Removal Certificates (CORCs). Carbon Future and Puro Earth are the two current markets for biochar carbon removal credits and LCA is required for validation and certification. In this work, LCA was conducted according to ISO 14044:2006, ISO 14067:2018 and Puro Earth Annex A: Biochar Methodology to determine and compare the carbon footprint associated with the production of biochar derived from woody feedstocks, from cradle-to-grave, utilizing large scale biochar production facilities employing different technologies. The functional unit is one metric tonne of biochar, and the primary function is soil conditioning and carbon sequestration. The system boundaries for the cradle-to-grave LCA include transporting waste biomass to conversion facility, processing the biomass into biochar using the conversion technology, drying and packaging the final biochar product, transportation to end-user, and product utilization. The system boundaries are defined by a specific methodology, as waste biomass is transported to the conversion facility for processing. GaBi LCA software was used to conduct the life cycle analysis with information gathered from specific industry and regional databases. The carbon footprint is expressed in tonne CO2-eq. and includes all greenhouse gases, directly and indirectly, related to the process. The end result of the net carbon sequestration is in the form of net carbon dioxide removal certificates (CORCs) resulting from biochar production activity as provided by Puro Earth which can then be monetized and marketed to be purchased by CO2 emitters for offset purposes. The CORCs for the different case-studies investigated were determined to be between 1.2 and 2.5 tonne CO2-eq. per tonne biochar. The LCA methodology developed in this work can easily be implemented to evaluate and validate the net CO2 removal equivalent credits offered by any biochar production technology.

This document is currently not available here.