scalable-step-step-approach-sustainable-bioplastic-production-from

Scalable Step-by-Step Approach of Sustainable Bioplastic Production from Food Waste

The global microplastic crisis, coupled with the growing challenges of food waste disposal, necessitates innovative solutions to address these ...

Quasar Energy Group

The effect of urea addition on giant reed ensilage and sequential anaerobic digestion (AD) of the ensiled giant reed was evaluated. The dry matter loss during ensilage (up to 90 days) with or without urea addition was about 1%. Addition of 2% urea enhanced production of lactic acid by about 4 times, and reduced production of propionic acid by 2-8 times. Besides, urea addition reduced degradation of cellulose and hemicellulose, and increased degradation of lignin in giant reed during ensilage. Ensilage with or without urea addition had no significant effects on the enzymatic digestibility of giant reed, but ensilage with urea addition achieved a cumulative methane yield of 173 L/kg VS, which was 18% higher than that of fresh giant reed. The improved methane yield of giant reed could be attributed to the production of organic acids and ethanol during ensilage.

Effect of urea addition on giant reed ensilage and subsequent methane production by anaerobic digestion.

Sequential batch thermophilic (55°C) solid-state anaerobic digestion (SS-AD) of yard trimmings was evaluated at a total solids (TS) content of 22% via recirculating digestate as the inoculum. The substrate-to-inoculum (S/I) ratio of 1 (TS basis) was favored over 2 and 3 due to significantly higher methane yield and volumetric productivity. At an S/I ratio of 1, sequential batch SS-AD gradually reached steady state by 3 runs (30days/run) with increases in both methane yields (up to 11.5%) and cellulose degradation (up to 55%), indicating that recirculated digestate could be a feasible inoculum to establish long term stable SS-AD of lignocellulosic biomass. The initial sharp increases of volatile fatty acids during runs 2-4 indicated faster hydrolysis of organic matter than during run 1, suggesting that microbes were probably more acclimated due to digestate recirculation. At steady state, 51% (w/w) of the digestate was recirculated as the inoculum.

Sequential batch thermophilic solid-state anaerobic digestion of lignocellulosic biomass via recirculating digestate as inoculum - Part I: Reactor performance.

This study aimed to investigate the effect of recirculation of digestate as inoculum on the microbial communities in thermophilic solid-state anaerobic digestion (SS-AD) of yard trimmings. The SS-AD consisted of 4 consecutive runs (30days/run), with digestate from the previous run being used as the inoculum of the subsequent run. Bacterial and archaeal communities (day 0, 4, 8, 12, 20, and 30) were examined using Illumina sequencing of 16S rRNA genes. The results revealed substantial microbial succession toward increased diversity until run 3. The proportions of Firmicutes that contained cellulolytic bacteria doubled, which might explain the concomitantly increased cellulose degradation and volatile fatty acids (VFAs). Clostridia and Thermotogae appeared to correlate with VFAs. The VFA accumulation likely induced dynamic shifts of methanogens, particularly to hydrogenotrophic Methanothermobacter, implying that non-acetoclastic oxidative pathway dominated during the steady-state thermophilic SS-AD. This study suggested that recirculating SS-AD digestate might be an effective way for inoculation.

Sequential batch thermophilic solid-state anaerobic digestion of lignocellulosic biomass via recirculating digestate as inoculum - Part II: Microbial diversity and succession.

NaOH pretreatment with leachate reuse and Ca(OH) pretreatment were compared for improved enzymatic digestibility and biogas production from giant reed, a promising energy crop. The NaOH pretreatment with leachate reuse increased glucose yields during enzymatic hydrolysis by 2.6-fold, and methane yields during anaerobic digestion by 1.4- to 1.6-fold. However, NaOH pretreatment had a negative net benefit (i.e., revenue from increased energy production minus chemical cost). Pretreatment with 7-20% Ca(OH) not only improved glucose yield and methane yield by up to 2.3-fold and 1.4-fold, respectively, but also obtained a net benefit of $1.1-5.8/tonne dry biomass. Thus, Ca(OH) pretreatment was shown to be more feasible than NaOH pretreatment for biogas production from giant reed.

Comparison of sodium hydroxide and calcium hydroxide pretreatments of giant reed for enhanced enzymatic digestibility and methane production.

The disposal of large amounts of food waste has caused significant environmental pollution and financial costs globally. Compared with traditional disposal methods (i.e., landfilling, incineration, and composting), anaerobic digestion (AD) is a promising technology for food waste management, but has not yet been fully applied due to a few technical and social challenges. This paper summarizes the quantity, composition, and methane potential of various types of food waste. Recent research on different strategies to enhance AD of food waste, including co-digestion, addition of micronutrients, control of foaming, and process design, is discussed. It is envisaged that AD of food waste could be combined with an existing AD facility or be integrated with the production of value-added products to reduce costs and increase revenue. Further understanding of the fundamental biological and physicochemical processes in AD is required to improve the technology.

Anaerobic digestion of food waste - Challenges and opportunities.

Solid-state anaerobic digestion (SS-AD) and composting are two potential alternatives to divert yard trimmings from landfills. This study aimed to evaluate the techno-economic feasibility of commercial-scale SS-AD and composting systems (20,000 metric tons (MT)/year) that received both yard trimmings and liquid AD effluent using a modeling software, SuperPro Designer. Both the SS-AD and composting systems were shown to be economically feasible. While their revenues were comparable ($48/MT), SS-AD with digestate drying showed a higher capital cost ($256/MT vs. $84/MT) but a lower non-facility-dependent operating cost ($11/MT vs. $21/MT) than composting. The payback time, internal rate of return (IRR), and net present value (NPV) were estimated to be ∼10 years, 8%, and $0.2 million, respectively, for SS-AD, and ∼4.9 years, 33%, and $1.8 million, respectively, for composting. Digestate drying was necessary to make SS-AD profitable via the sale of byproduct, but it was also the most energy intensive step, relying on heat recovery to reduce costs. Moreover, the economics of SS-AD were highly improved (NPV $2 million) with financial incentives (i.e. investment tax credits), indicating that incentives were critical to the economic feasibility of current SS-AD systems that utilize lignocellulosic biomass. However, renewable identification numbers (RINs) and renewable energy certificates (RECs) had minor effects. Furthermore, the economics of both systems were most sensitive to plant size, tipping fees, and byproduct/compost price. The results suggest SS-AD may be favored for centralized management while composting for de-centralized management of yard trimmings. Alternative ways to valorize digestate should be evaluated in future studies.

Techno-economic analyses of solid-state anaerobic digestion and composting of yard trimmings.

Giant reed was the first time used for photo-fermentative hydrogen production with HAU-M1 bacteria. Effects of NaOH and Ca(OH) pretreatments of giant reed on structural changes, enzymatic digestibility, hydrogen production, and energy conversion efficiency were evaluated. Compared to Ca(OH) pretreatment, NaOH pretreatment removed more dry matter and lignin at the same loading. The highest glucose yield (44.9%) of NaOH pretreatment was 1.74-fold higher than that of Ca(OH) pretreatment. 20% NaOH pretreated giant reed biomass achieved the highest hydrogen yield (98.3 mL/g TS), which was 20% and 70% higher than the highest level of Ca(OH) pretreated (20% Ca(OH)) and untreated giant reed, respectively. Only giant reed biomass pretreated with 20% NaOH resulted in a significant (p < 0.05) increase (25%) in energy conversion efficiency.

Effect of alkaline pretreatment on photo-fermentative hydrogen production from giant reed: Comparison of NaOH and Ca(OH).

The complex interaction between nitrate (NO) reduction and fermentation is poorly understood when high levels of NO are introduced into anaerobic systems. This study investigated the competitive distribution between conventional denitrification (DEN) and dissimilatory nitrate reduction to ammonium (DNRA) during simultaneous denitrification and fermentation in arrested methanogenesis. Up to 62% of initial NO (200 mg-N/L) was retained as ammonium through DNRA at a chemical oxygen demand (COD)/N ratio of 25. Significant NO emission occurred (1.7 - 8.0% of the initial NO) with limited carbon supply (≤1600 mg COD/L) and sludge concentration (≤3000 mg COD/L). VFA composition shifted predominantly towards acetic acid (>50%) in the presence of nitrate. A novel kinetic model was developed to predict DNRA vs. DEN partitioning and NO accumulation. Overall, NO input, organic loading, and carbon source characteristics independently and collectively controlled competitive DNRA vs. DEN partitioning.

Competitive partitioning of denitrification pathways during arrested methanogenesis: Implications in ammonium recovery, NO emission, and volatile fatty acid production.

Article	Year
Effect of urea addition on giant reed ensilage and subsequent methane production by anaerobic digestion. Bioresource technology\| PubMed ID: 26094194	2015
Sequential batch thermophilic solid-state anaerobic digestion of lignocellulosic biomass via recirculating digestate as inoculum - Part I: Reactor performance. Bioresource technology\| PubMed ID: 28411490	2017
Sequential batch thermophilic solid-state anaerobic digestion of lignocellulosic biomass via recirculating digestate as inoculum - Part II: Microbial diversity and succession. Bioresource technology\| PubMed ID: 28637161	2017
Comparison of sodium hydroxide and calcium hydroxide pretreatments of giant reed for enhanced enzymatic digestibility and methane production. Bioresource technology\| PubMed ID: 28867429	2017
Anaerobic digestion of food waste - Challenges and opportunities. Bioresource technology\| PubMed ID: 28965912	2018
Techno-economic analyses of solid-state anaerobic digestion and composting of yard trimmings. Waste management (New York, N.Y.)\| PubMed ID: 30803595	2019
Effect of alkaline pretreatment on photo-fermentative hydrogen production from giant reed: Comparison of NaOH and Ca(OH). Bioresource technology\| PubMed ID: 32088626	2020
Competitive partitioning of denitrification pathways during arrested methanogenesis: Implications in ammonium recovery, NO emission, and volatile fatty acid production. Bioresource technology\| PubMed ID: 38642664	2024

Yebo Li

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