Effect of feed source and pyrolysis conditions on properties and metal sorption by sugarcane biochar

Authors: HASS, AMIR - West Virginia State University; Lima, Isabel

Submitted to: Environmental Technology & Innovation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2018
Publication Date: 2/3/2018
Citation: Hass, A., Lima, I.M. 2018. Effect of feed source and pyrolysis conditions on properties and metal sorption by sugarcane biochar. Environmental Technology & Innovation. 10:16-26. https://doi.org/10.1016/j.eti.2018.01.007.
DOI: https://doi.org/10.1016/j.eti.2018.01.007

Interpretive Summary: Sugarcane bagasse and sugarcane leaf residue represent the two largest by-products of sugarcane processing and harvesting, respectively. Louisiana is a major grower of sugarcane and effective value-added ways of reutilizing these large waste materials have yet to be developed. They are underutilized and for that reason were converted into value-added biochars, materials utilized for remediation applications. Development of low-cost sorbents like biochars from sugarcane bagasse and leaf residue for use in non-point-source runoff-water infiltration systems is essential for improving water quality. These biochars were effective at removing heavy metals from water, such as copper, cadmium and lead and the performance was influenced by the type of feedstock, the pyrolysis temperature and various physico-chemical properties measured. Inferences were made on relationships between key physico-chemical properties and the ability of these materials to remove heavy metals from solution. These sugarcane by-products can serve as a reliable and consistent feed source for development of biochars for removal of heavy metals from surface waters.

Technical Abstract: Population growth along with urbanization expansion and intensification of arable land management burdens natural systems ability to sustain ecosystem services such as clean waters. Development of low-cost sorbents for use in non-point-source runoff-water infiltration systems is essential for improving water quality. Residue of sugarcane industry can serve as a reliable and consistent feed source for development of biochars for removal of heavy metals from surface waters. Sugarcane biomass from different feed source residues of sugar mill operation were collected and used in production of biochar at different temperatures (350, 500, 650, and 800 °C) and with/out steam activation. Feed sources included: a. fresh cane and leafy trash residue removed by a de-trasher machine installed at the front-end of the mill to remove leafy and field residues from the cane billets entering the plant; b. fresh sugarcane bagasse collected right after the milling process, and c. old bagasse collected from a pile left outside the plant for several years. Biochar yield, composition, and physical properties were determined, and metal sorption capacity evaluated by fitting sorption isotherm results to non-linear Langmuir equation. Ash content of feed source material follow the order fresh cane trash (23%) > old bagasse (15%) > fresh bagasse (5%). Pyrolysis more than doubled biochar ash content and was 2 to 3 times higher for fresh cane trash and old bagasse than for fresh bagasse biochars. On the other hand, surface area of fresh bagasse activated biochars (493 m2 g-1) was nearly twice as high as that of the old bagasse (262 m2 g-1), or fresh cane trash (204 m2 g-1) biochars. Cadmium sorption capacity increased upon activation and was an order of magnitude higher for old bagasse biochars than for fresh bagasse or fresh cane trash biochars (ranging from 43.4 to 63.8 mg g-1 compared to 0.35 to 0.47 mg g-1, or 4.35 to 6.29 mg g-1, respectively). Maximum sorption capacity for Cd and Cu was highly correlated with biochar ash content, while that of Pb correlated with biochar surface area and total sulfur content. Cu sorption capacity inversely correlated to O/C ratio and reduced significantly upon acid washing of activated and non-activated 500 °C old bagasse biochars (from 32.2 to 14.3 mg g-1 and from 3.88 to 0.00, all respectively). Overall, ash content seemed to play a decisive role in metal sorption capacity of sugarcane bagasse biochars.