Lignin - Potential Sources for Carbon Nagative Building Materials

Z. Cai, Q. Yan
Forest Products Laboratory,
United States

Keywords: lignin, foam, insulation, carbon


Abstract To make a zero or negative carbon buildings, carbon-negative materials are desperately needed. Biomass absorbs from the atmosphere and fixes CO2 in a stable form as a plant. Therefore, biomass and its derivative products are considered as carbon-negative materials. Lignin is one of the major components of lignocellulosic biomass and the most important natural phenolic polymer. It is a wood by-product composed of 60-65wt% carbon with an annual production over 70 million tons worldwide from the paper and pulping industries. USFS Forest Products Laboratory and Ligwood LLC have developed a method to produce open-cell self-expanding foams from Kraft lignin and recycled waste polymers. The foaming process can be performed under a temperature range of 150-250 C by pressing mold or extruding process. Our process demonstrates high lignin conversion (~100% carbon in lignin is kept in foam products) and lignin foam yield (90-95% lignin mass is kept in foam product). About 3.5 – 4.0 m3 lignin foam can be produced from 1-ton raw Kraft lignin. No catalysts, blowing agents, surfactants or solvents are used in the foaming process. The resultant self-expanding foam has high lignin content (85 - 95% by mass) and a tunable open-cell structure. Densities of the self-expanding foam products are generally in the range of about 0.2 g/cm3 to 0.5 g/cm3. Our preliminary results showed that the self-expanding foams exhibited compressive strengths of up to about 50 MPa. The thermal conductive coefficients of lignin foams were in the range of about 0.03 kw/m to 0.3 kw/m which were comparable to the current polyurethane foams.