|Posted by The IBEST on 9 July, 2016 at 4:50|
A team of researchers at the Universities of Surrey and Bath in the UK has discovered an effective way of adding value and increasing sustainability of waste resources, by the recovery of metals, extractives, chemicals, fertiliser and energy.
The findings are published in Bioresource Technology, 215, 131-143, 2016: “Novel integrated mechanical biological chemical treatment (MBCT) systems for the production of levulinic acid from fraction of municipal solid waste: A comprehensive techno-economic analysis” selected as the best article. Researchers have been speaking in isolation about chemical production, metal recovery and energy generation for sustainability and a circular economy. However, it looked far from reality to achieve all these productions using integrated configuration such as biorefinery.
The findings under the NERC programme: Resource Recovery from waste (RRfW) are published in: Bioresource Technology, 215, 131-143, 2016. The paper has been selected as the best article amongst all published in the Special Issue “Waste Biorefinery – Advocating Circular Economy” of Bioresource Technology, Volume 215, 1-396, Elsevier, 2016. Figure 1 in the article showing the simulation flowsheet of levulinic acid production features on the cover page of the Special Issue.
The article reports integrated conceptual biorefinery systems for unlocking the value of organics in municipal solid waste (MSW) through the production of levulinic acid (by only 5 wt%) that increases the economic margin by 110-150%. The price of levulinic acid is 5-8 Euro/kg compared to bioethanol, 0.3-0.5 Euro/kg. Highly integrated process scheme eliminates the need for any subsidies including gate fees. Based on source segregated municipal solid waste, oil palm, sugarcane and agave residues, priced at 50 Euro/t, 43-300 Euro/t value can be generated.
Bio-based products from waste can offset fossil fuels by displacing equivalent products. Bio-based products can contribute to greater than 40% of the total greenhouse gas emission cut by the biorefinery system, which is over 90% compared to equivalent petroleum based system.
Levulinic acid offers many functionalities of petrochemicals and is a precursor to numerous added value pharmaceutical, specialty chemical, agricultural, solvent, platform chemical and fuel additive products. Levulinic acid is one of few molecules referred as ‘sleeping giants’ owing to their vast potentials in the emerging bio-based economy due to their key positions in the production of biomass-derived intermediates and transition from fossil based economy to bio- renewable- based circular economy.
Levulinic acid has emerged as a niche platform chemical in production of pharmaceutical: δ-aminolevulinic acid, specialty chemical: γ-valerolactone, agricultural: diphenolic acid, platform chemical: pyrrolidones, succinic acid and fuel additive: levulinate esters, 2-methyltetrahydrofuran with addressable petrochemical replacement potential to be over 25 million tonne by 2020.
After mechanical separation recovering recyclables, metals (iron, aluminium, copper) and refuse derived fuel (RDF), lignocelluloses from remaining MSW are extracted by supercritical-water for chemical valorisation, comprising hydrolysis in 2 wt% dilute H2SO4 catalyst producing LA, furfural, formic acid, via C5/C6 sugar extraction, in plug flow (210−230°C, 25 bar, 12 s) and continuous stirred tank (195−215°C, 14 bar, 20 mins) reactors; char separation and LA extraction/purification by methyl isobutyl ketone solvent; acid/solvent and by-product recovery. The by-product and pulping effluents are anaerobically digested into biogas and fertiliser. Produced biogas (6.4 MWh/t), RDF (5.4 MWh/t), char (4.5 MWh/t) are combusted, heat recovered into steam generation in boiler; on-site heat/steam demand is met; balance of steam is expanded into electricity in steam turbines.
The most substantial challenges to overcome were the development of new process that integrates RRfW and biorefinery configurations, to sustainably replace petroleum with biomass. The integration is needed to mitigate i) negative effects of impurities in heterogeneous waste feedstock on reaction-separation process yields and thereby to give flexibility in feedstock processing, and ii) environmental and health impacts by transforming pollutants into valuable resources, and to achieve total site energy optimisation such that the integrated system is a net energy source. The highly integrated and effective process is not selective in the choice of feedstocks because RRfW removes and recovers impurities as resources prior to chemical valorisation of organic fraction. Hence, biomass supply and choice is not a constraint for chemical valorisation. Flexibility in processing a whole range of biomass allows uninterrupted production lines. The process can be fully automated with online analytical, monitoring and control systems for optimal trouble-free reliable operations throughout the year.
Publication: Sadhukhan J., Ng K.S. and Martinez-Hernandez E. Novel integrated mechanical biological chemical treatment (MBCT) systems for the production of levulinic acid from fraction of municipal solid waste: A comprehensive techno-economic analysis. Bioresource Technology, 215, 131-143, 2016. doi:10.1016/j.biortech.2016.04.030