Life Cycle Assessment of Hempstone for Green Buildings

Abstract

Hemp is a non-psychoactive (less than 1 % tetrahydrocannabinol) variety of Cannabis sativa L. It is cultivated on hills and used mainly for textiles. Hemp requires less water and pesticides. It grows fast (3 - 4 m in 3 months) and has a high carbon sequestration rate of 1.67 kg CO₂-eq per kg of hemp fibre. The local hemp in Thailand is the Rpf3 species developed by the Highland Research and Development Institute. This study aims at exploring the potential use of hemp for eco-building materials to meet the increasing demands for green buildings by applying the upcycling design concept. Hemp stalks left after fibre harvesting were sun dried before ground into small pieces of varying sizes. Artificial stones (polyester-resin solid surface material) left over from production processes were also collected. Hemp materials and artificial stone scraps were used at different proportions to develop a new composite called Hempstone. The study found that Hempstone did not require the drying process; hemp fibers helped absorb the moisture. Hemp fibres also offered unique natural aesthetic. Quality tests were conducted to ensure that Hempstone was fit for use in construction. Life Cycle Assessment (LCA) was performed to identify the potential reduction of environmental impacts of typical artificial stone and Hempstone. The results indicated that the Hempstone sheet (0.82 x 3.04 x 0.012 m) with 10 % of hemp-stalks (6 - 10 mm size) and 7.5 % or 10 % by weight of artificial stone scraps performed best with the potential reduction of environmental impacts by 40 % on climate change, 42 % on freshwater eutrophication, 55 % on terrestrial eco-toxicity and 60 % on terrestrial eco-toxicity. With the growing pursuit of green buildings, these reductions show that the potential use of hemp in local eco-building materials to help reducing impact on the environment.