Utilization of Lignin from the Waste of Bioethanol Production as a Mortar Additive

Abstract

Lignin is the second most abundant biopolymer, exceeded only by cellulose, and comprises 15-25% of the dry weight of woody plants, with around 285,000 tons/year of production capacity globally. This study aims to utilize the lignin obtained from the waste of bioethanol production from oil palm empty fruit bunches (OPEFB) as a mortar additive. The use of mortar as a material for road construction is increasing, but its long time hardening is causing problems such as traffic jams. Lignin can be used as an additive to shorten the hardening time of mortar. Lignin was isolated at various NaOH concentrations and temperatures of OPEFB pretreatment for bioethanol production. The workability of the slump and compressive strength of mortars generated were further tested. Lignin from OPEFB can be used as a water reducer in the mortar with improved workability as much as 24.4% compared to controls. The addition of lignin could also increase the compressive strength at the mortar age of 7 and 28 days compared to the commercial lignosulfonate and control on the various water-cement ratios. The setting time of mortar with the lignin addition increased rapidly, reaching up to 80% at the 7 days, indicating that curing time is getting shorter. The most remarkable improvement of compressive strength with suitable workability and high-quality concrete was reached by 1% lignin addition and 0.45 water-cement ratio with compressive strength 38.81 N/mm2 at 28 days. Keywords: compressive strength, lignin, mortar, OPEFB, water reducer