Comparison of Novel Biochars and Steam Activated Carbon from Mixed Conifer Mill Residues

Nathaniel Anderson,Hongmei Gu,Richard Bergman

doi:10.3390/en14248472

Nathaniel Anderson, Hongmei Gu + Show 1 more

Open Access

https://doi.org/10.3390/en14248472

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Abstract

There is increasing demand in environmental remediation and other sectors for specialized sorbents made from renewable materials rather than hard coals and minerals. The proliferation of new pyrolysis technologies to produce bio-based energy, fuels, chemicals, and bioproducts from biomass has left significant gaps in our understanding of how the various carbonaceous materials produced by these systems respond to processes intended to improve their adsorption properties and commercial value. This study used conventional steam activation in an industrial rotary calciner to produce activated carbon (AC) from softwood biochars made by three novel pyrolysis systems. Steam was injected across four heating zones ranging from 816 °C to 927 °C during paired trials conducted at calciner retention times of 45 min and 60 min. The surface area of the three biochars increased from 2.0, 177.3, and 289.1 m2 g−1 to 868.4, 1092.9, and 744.8 m2 g−1, respectively. AC iodine number ranged from 951 to 1218 mg g−1, comparing favorably to commercial AC produced from bituminous coal and coconut shell. The results of this study can be used to operationalize steam activation as a post-processing treatment for biochar and to expand markets for biochar as a precursor in the manufacture of specialized industrial sorbents.

Highlights

All three biochars met the standards for biochar chemical characteristics as determined by IBI and European Biochar Certificate (EBC) [10,11]
But remain relatively small compared to markets for activated carbon and other industrial adsorbents
It has been frequently proposed including by the authors [15,16,32], that biochar can be used as an effective and potentially cost competitive substitute for these products or as a precursor in the manufacture of specialized sorbents, especially in cases where bio-based products are preferred over coal and mineral products because they have lower life cycle environmental impacts as measured by their carbon footprint [15]

Summary

Introduction

Biochar is an anthropogenic pyrogenic carbonaceous material used as a soil amendment It can be made from biomass using a wide range of methods, from wooden ricks, earth mound kilns, and small portable flame-cap kilns to large-scale industrial pyrolysis systems. In all cases, it is the product of the thermal decomposition of biomass in an inert or low oxygen atmosphere, which removes volatile compounds and leaves a high-carbon char. Not directly related to improving soils for plant growth, include carbon sequestration and waste management as well as benefits from the renewable energy and fuel products that are coproduced by some pyrolysis systems [2]. Compared to conventional charcoal manufacturing, which is often focused on making solid fuels for combustion, many of the advanced pyrolysis systems that produce biochar are designed to simultaneously meet soil, waste management, climate, and energy objectives [3]

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