Issue 13, 2023

Lactic acid and biomethane production from bread waste: a techno-economic and profitability analysis using pinch technology

Abstract

Lactic acid (LA) is a vital platform chemical with diverse applications, especially for biodegradable polylactic acid. Bread waste (BW) is sugar-rich waste biomass generated in large quantities in residential and commercial operations. Recently, we evaluated the potential of BW for LA production by Bacillus coagulans under non-sterile conditions. This work presents a techno-economic and profitability analysis for valorizing 100 metric tons of BW per day to alleviate environmental pollution with concurrent production of LA and biomethane. We compared two fermentation approaches: acid-neutral (Scenario I) and low pH (Scenario II). Traditional esterification with methanol, followed by hydrolysis of methyl lactate, was employed for downstream separation to obtain polymer-grade LA. High-pressure steam was generated from solid debris via anaerobic digestion to complement energy demands partly. Energy consumption was further attenuated by process integration using pinch technology, with around 15% and 11% utility cost savings for Scenario I and II, respectively. These processes were capital-intensive, with 42–46% of LA production cost stemming from direct and indirect costs. Utilities were the major cost-contributing factor (19–21%) due to energy-intensive water evaporation from dilute fermentation broth. Due to additional processing steps, capital investment and operating costs were slightly higher in Scenario I than in Scenario II. LA manufacturing cost was thus more for Scenario I ($2.07 per kg) than Scenario II ($1.82 per kg). The minimum LA selling price for Scenario I and II were $3.52 and $3.22 per kg, respectively, with five-year payback periods and 8.5% internal rates of return. LA was slightly more expensive for decentralized BW processing than the market price.

Graphical abstract: Lactic acid and biomethane production from bread waste: a techno-economic and profitability analysis using pinch technology

Supplementary files

Article information

Article type
Paper
Submitted
31 1 2023
Accepted
29 5 2023
First published
07 6 2023
This article is Open Access
Creative Commons BY-NC license

Sustainable Energy Fuels, 2023,7, 3034-3046

Lactic acid and biomethane production from bread waste: a techno-economic and profitability analysis using pinch technology

S. Mailaram, V. Narisetty, S. K. Maity, S. Gadkari, V. K. Thakur, S. Russell and V. Kumar, Sustainable Energy Fuels, 2023, 7, 3034 DOI: 10.1039/D3SE00119A

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