Fruit-vegetable Waste Research Articles

Determination and evaluation of biogas and methane productions of vegetable and fruit wastes with Hohenheim Batch Test method

Nowadays, biogas technology applications are gradually increasing worldwide due to the economic and environmental benefits. Many researches and studies related to the determination of the biogas potential of organic waste materials have been carried out in the recent years. Studies to determine the specific methane potential of organic waste materials have a great importance for both design and economical operation of the biogas plants. Energy potential that will be recovered from organic wastes is substantial in Turkey. Thanks to biogas plants gathering vegetable-fruit wastes and other organic wastes are planned to produce significant amount of renewable energy in Turkish markets. Owing to the use of organic wastes, the disposal of waste as well as energy production, soil, water and air pollution in terms of environmental protection are also minimized. On the other hand, the organic wastes produced from plants can also be utilized as fertilizer in vegetable production. In this study, the cumulative biogas and methane production of vegetable and fruit wastes were experimentally determined with HBT (Hohenheim Batch Test) method. Biogas and methane yields of vegetable and fruit wastes were found as 0.54-0.73 Nm3/(kg ODM) and 0.29-0.37 Nm3/(kg ODM), respectively. The highest value of the cumulative specific methane production was tomato wastes (0.37 Nm3/(kg ODM)), and the lowest value was lettuce wastes (0.29 Nm3/(kg ODM)), as well. The average cumulative specific methane production values of mixed vegetable and fruit wastes are determined as 0.34 Nm3/(kg ODM). Keywords: biogas, methane production, Hohenheim Batch Test, vegetable and fruit wastes, renewable energy, Turkey DOI: 10.25165/j.ijabe.20171004.2864 Citation: Aybek A,Ucok S. Determination and evaluation of biogas and methane productions of vegetable and fruit wastes with Hohenheim Batch Test method Int J Agric & Biol Eng, 2017; 10(4): 207–215.

Determination and evaluation of biogas and methane productions of vegetable and fruit wastes with Hohenheim Batch Test method

Nowadays, biogas technology applications are gradually increasing worldwide due to the economic and environmental benefits. Many researches and studies related to the determination of the biogas potential of organic waste materials have been carried out in the recent years. Studies to determine the specific methane potential of organic waste materials have a great importance for both design and economical operation of the biogas plants. Energy potential that will be recovered from organic wastes is substantial in Turkey. Thanks to biogas plants gathering vegetable-fruit wastes and other organic wastes are planned to produce significant amount of renewable energy in Turkish markets. Owing to the use of organic wastes, the disposal of waste as well as energy production, soil, water and air pollution in terms of environmental protection are also minimized. On the other hand, the organic wastes produced from plants can also be utilized as fertilizer in vegetable production. In this study, the cumulative biogas and methane production of vegetable and fruit wastes were experimentally determined with HBT (Hohenheim Batch Test) method. Biogas and methane yields of vegetable and fruit wastes were found as 0.54-0.73 Nm3/(kg ODM) and 0.29-0.37 Nm3/(kg ODM), respectively. The highest value of the cumulative specific methane production was tomato wastes (0.37 Nm3/(kg ODM)), and the lowest value was lettuce wastes (0.29 Nm3/(kg ODM)), as well. The average cumulative specific methane production values of mixed vegetable and fruit wastes are determined as 0.34 Nm3/(kg ODM). Keywords: biogas, methane production, Hohenheim Batch Test, vegetable and fruit wastes, renewable energy, Turkey DOI: 10.25165/j.ijabe.20171004.2864 Citation: Aybek A,Üçok S. Determination and evaluation of biogas and methane productions of vegetable and fruit wastes with Hohenheim Batch Test method Int J Agric & Biol Eng, 2017; 10(4): 207–215.

DOMATES ATIKLARININ BIYOGAZ DEĞERLERININ

Nowadays, biogas technology applications are gradually increasing worldwide due to the economic and environmental benefits. Many researches and studies related to the determination of the biogas potential of waste organic materials have been carried out in the recent years. Studies to determine the specific methane potential of organic waste materials have a great importance for both design and economical operation of the biogas plants.Energy potential that will be recovered from organic wastes are substantial in our country.Thanks to biogas plants gathering vegetable-fruit wastes and other organic wastes are planned to produce significant amount of renewable energy in our country markets. Owing to the use of organic wastes, the disposal of waste as well as energy production, soil, water, air pollution in terms of environmental protection are also minimized. On the other hand, the organic wastes produced from plants can also be utilised as fertilizer in vegetable production. In this study, the cumulative biogas and methane productions of tomato wastes were experimentally determined with HBT (Hohenheim Batch Testing) method. Biogas and methane yields of tomato wastes were found as 0.687-0.695 Nm3/kg OKM and 0.364-0.374 Nm3/kg OKM respectively. Obtained results for biogas production has importance.

Design and cost-benefit analysis of a novel anaerobic industrial bioenergy plant in Pakistan

The design and Cost-benefit analysis (CBA) of a novel anaerobic bioenergy plant is presented. This plant can digest various feed sources including animal-manure, vegetable-fruit wastes, poultry wastes, sugar molasses etc. The fixed dome multi-digestor system enables a continuous feed and flow mechanism. It is also equipped with a biogas purification, compression and storage system. This medium scale bioenergy plant is the first of its kind in Pakistan. It has a total installation cost of US$105,000 and annual operation and maintenance cost of US$23,400. The average energy production is 142,380 kWh per annum. With a current average energy cost of US$0.315 per kWh from all sources in Pakistan, the cost-benefit ratio is 1.2 at an internal rate of return (IRR) of 19.76%, and short payback period.

Determination of the effect of C/N ratio on composting of vegetable-fruit wastes

In this study, vegetable-fruit wastes were composted aerobically and the effect of various C/N ratios on the process was determined. Eight reactors with various initial C/N ratios were used. Moisture, temperature, pH, electrical conductivity (EC), C/N and cellulose were investigated during process. Moisture levels did not changed significantly by the various C/N. Among the highest temperatures reached in the reactors, the lowest ones were seen in the reactors those had the lowest C/N. The reactors with lower C/N were generally stayed at thermophilic phase shorter than the reactors which had higher C/N. The highest decrease in C/N was seen in the reactor that had an initial C/N of 25 and the lowest decrease in C/N was seen in the reactor that had the lowest initial C/N. The reactors which had higher initial C/N than the other reactors had generally lower pH values than the others. The reactor which had the lowest initial C/N had the highest pH values at the beginning of the thermophilic phase. Initial ECs in the reactors with lower C/N were higher than the others. Various C/N ratios significantly effected the cellulose contents during the process.

Producing Methane Enriched Biogas using Solvent Absorption Method

Waste-to-energy (WTE) production is one of the sustainable solutions to fulfill energy demands and minimize the environmental problems associated with waste landfilling. This work investigates the biogas production and methane (CH4) enrichment for anaerobic digestion (AD) of fruit and vegetable waste (FVW). The effect of pH and temperature were studied using a lab scale batch anaerobic digester. The raw biogas was pebbled through water, NaOH, Ca(OH)2 and triethanolamine (TEA) for biogas purification and CH4 enrichment. The results showed that mixed fruit waste (MFW) provides 10 % more biogas yield than mixed fruit vegetable waste (MFVW). The maximum biogas yield of 0.030 (g/g volatile solids) was achieved at thermophilic temperature (TT). The optimum pH range under mesophilic temperature (MT) and TT condition was in between 8.3 - 8.8. The use of NaOH, Ca(OH)2 and TEA increased CH4 enrichment upto 5 %, 9 % and 7 %. Biogas having 71 % CH4 contents with 28 % reduced CO2 and 150 ppm H2S was produced using Ca(OH)2.

Microbial community structures in an integrated two-phase anaerobic bioreactor fed by fruit vegetable wastes and wheat straw

The microbial community structures in an integrated two-phase anaerobic reactor (ITPAR) were investigated by 16S rDNA clone library technology. The 75L reactor was designed with a 25L rotating acidogenic unit at the top and a 50L conventional upflow methanogenic unit at the bottom, with a recirculation connected to the two units. The reactor had been operated for 21 stages to co-digest fruit/vegetable wastes and wheat straw, which showed a very good biogas production and decomposition of cellulosic materials. The results showed that many kinds of cellulose and glycan decomposition bacteria related with Bacteroidales, Clostridiales and Syntrophobacterales were dominated in the reactor, with more bacteria community diversities in the acidogenic unit. The methanogens were mostly related with Methanosaeta, Methanosarcina, Methanoculleus, Methanospirillum and Methanobacterium; the predominating genus Methanosaeta, accounting for 40.5%, 54.2%, 73.6% and 78.7% in four samples from top to bottom, indicated a major methanogenesis pathway by acetoclastic methanogenesis in the methanogenic unit. The beta diversity indexes illustrated a more similar distribution of bacterial communities than that of methanogens between acidogenic unit and methanogenic unit. The differentiation of methanogenic community composition in two phases, as well as pH values and volatile fatty acid (VFA) concentrations confirmed the phase separation of the ITPAR. Overall, the results of this study demonstrated that the special designing of ITPAR maintained a sufficient number of methanogens, more diverse communities and stronger syntrophic associations among microorganisms, which made two phase anaerobic digestion of cellulosic materials more efficient.

Anaerobic co-digestion of kitchen waste and fruit/vegetable waste: Lab-scale and pilot-scale studies

The anaerobic digestion performances of kitchen waste (KW) and fruit/vegetable waste (FVW) were investigated for establishing engineering digestion system. The study was conducted from lab-scale to pilot-scale, including batch, single-phase and two-phase experiments. The lab-scale experimental results showed that the ratio of FVW to KW at 5:8 presented higher methane productivity (0.725L CH4/g VS), and thereby was recommended. Two-phase digestion appeared to have higher treatment capacity and better buffer ability for high organic loading rate (OLR) (up to 5.0g(VS)L−1d−1), compared with the low OLR of 3.5g(VS)L−1d−1 for single-phase system. For two-phase digestion, the pilot-scale system showed similar performances to those of lab-scale one, except slightly lower maximum OLR of 4.5g(VS)L−1d−1 was allowed. The pilot-scale system proved to be profitable with a net profit of 10.173$/ton as higher OLR (⩾3.0g(VS)L−1d−1) was used.

Selective adaptation of an anaerobic microbial community: Biohydrogen production by co-digestion of cheese whey and vegetables fruit waste

The co-digestion process of crude cheese whey (CCW) with fruit vegetable waste (FVW) for biohydrogen production was investigated in this study. Five different C/N ratios (7, 17, 21, 31, and 46) were tested in 2 L batch systems at a pH of 5.5 and 37 °C. The highest specific biohydrogen production rate of 10.68 mmol H2/Lh and biohydrogen yield of 449.84 mL H2/g COD were determined at a C/N ratio of 21. A pyrosequencing analysis showed that the main microbial population at the initial stage of the co-digestion consisted of Bifidobacterium, with 85.4% of predominance. Hydrogen producing bacteria such as Klebsiella (9.1%), Lactobacillus (0.97%), Citrobacter (0.21%), Enterobacter (0.27%), and Clostridium (0.18%) were less abundant at this culture period. The microbial population structure was correlated with the lactate, acetate, and butyrate profiles obtained. Results demonstrated that the co-digestion of CCW with FVW improves biohydrogen production due to a better nutrient balance and improvement of the system's buffering capacity.

A half-submerged integrated two-phase anaerobic reactor for agricultural solid waste codigestion

Anaerobic digestion is widely used in bioenergy recovery from waste. In this study, a half-submerged, integrated, two-phase anaerobic reactor consisting of a top roller acting as an acidogenic unit and a recycling bottom reactor acting as a methanogenic unit was developed for the codigestion of wheat straw (WS) and fruit/vegetable waste (FVW). The reactor was operated for 21 batches (nearly 300d). Anaerobic granular sludge was inoculated into the methanogenic unit. The residence time for the mixed waste was maintained as 10d when the operation stabilized, and the temperature was kept at 35°C. The highest organic loading rate was 1.37kg VS/(m3d), and the maximum daily biogas production was 328L/d. Volatile solid removal efficiencies exceeded 85%. WS digestion could be confirmed, and efficiency was affected by both the ratio of WS to FVW and the loading rate. The dominant bacteria were Bacteroides-like species, which are involved in glycan and cellulose decomposition. Methanogenic community structures, pH levels, and volatile fatty acid concentrations in the acidogenic and methanogenic units differed, indicating successful phase separation. This novel reactor can improve the mass transfer and microbial cooperation between acidogenic and methanogenic units and can efficiently and steady codigest solid waste.

Integration of fermentative biohydrogen with methanogenesis from fruit–vegetable waste using different pre-treatments

Fruit–vegetable waste was subjected to three different pre-treatments to enrich the two-stage biofuel production potential. The fluorescence excitation–emission matrix (EEM) spectra coupled with parallel factor (PARAFAC) analysis and fluorescence regional integration analysis were utilised to investigate dissolved organic matter degradation during two-stage fermentation process. The results showed that compared with that of alkali and enzyme pre-treatments, the acid pre-treatment resulted in the maximum biogas production rates and proportion in the hydrogenogenic stage (10.11mL/h, 41.2% hydrogen) when combined with the methanogenic process (4.67mL/h, 76.1% methane). In addition, the analysis of soluble metabolites composition indicated that both ethanol- and butyric acid-type fermentation processes had taken place as a result of acid pre-treatment, whereas only butyric acid-type fermentation resulted from alkali and enzyme pre-treatments. The PARAFAC analysis modelling of the EEM spectra revealed three fluorescent components in the effluents of three fermentation stages and assumed that the projected characteristic value may be used as a rapidly obtained indicator for substrate degradation and system stability of a two-stage biofuel production process.

Biohydrogen Production Based on the Evaluation of Kinetic Parameters of a Mixed Microbial Culture Using Glucose and Fruit–Vegetable Waste as Feedstocks

Hydrogen (H2) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H2 production obtained were successfully adjusted by a logistic model. The kinetic parameters (μ max = 0.101h(-1), K s = 2.56g/L) of an H2-producing microbial culture determined by the Monod and Haldane-Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H2 production of 700mL was attained. The feasibility of producing H2 from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H2 production and waste organic material degradation was determined. The highest H2 production rate (1.7mmol/day), the highest cumulative H2 volume (310mL), and 25% chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37g COD/L. The lowest H2 production rates were obtained with relatively low initial substrate concentrations of 5 and 11g COD/L. The H2 production rates with FVW were also characterized by the logistic model. Similar cumulative H2 production was obtained when glucose and FVW were used as substrates.

Effect of thermal hydrolysis pre-treatment on anaerobic digestion of municipal biowaste: A pilot scale study in China

Co-digestion of wasted sewage sludge, restaurant kitchen waste, and fruit-vegetable waste was carried out in a pilot plant with thermal hydrolysis pre-treatment. Steam was used as heat source for thermal hydrolysis. It was found 38.3% of volatile suspended solids were dissolved after thermal hydrolysis, with digestibility increased by 115%. These results were more significant than those from lab studies using electricity as heat source due to more uniform heating. Anaerobic digesters were then operated under organic loading rates of about 1.5 and 3 kg VS/(m³ d). Little difference was found for digesters with and without thermal pre-treatment in biogas production and volatile solids removal. However, when looking into the digestion process, it was found digestion rate was almost doubled after thermal hydrolysis. Digester was also more stable with thermal hydrolysis pre-treatment. Less volatile fatty acids (VFAs) were accumulated and the VFAs/alkalinity ratio was also lower. Batch experiments showed the lag phase can be eliminated by thermal pre-treatment, implying the advantage could be more significant under a shorter hydraulic retention time. Moreover, it was estimated energy cost for thermal hydrolysis can be partly balanced by decreasing viscosity and improving dewaterability of the digestate.

Co-digestion of kitchen waste and fruit–vegetable waste by two-phase anaerobic digestion

The high salinity and fat contents of kitchen waste (KW) inhibits the effect of two-phase anaerobic digestion system. This research introduces fruit-vegetable waste (FVW) to alleviate the inhibition effect caused by salinity and fat concentrations, and tries to achieve an optimal addition ratio of FVW, an optimal hydraulic remain time (HRT) of acidogenic-phase reactor and methanogenic-phase reactor. A two-phase anaerobic digestion (AD) system was developed to co-dispose KW and FVW. Four sets of experiments were run with different mass proportions between KW and FVW (25-75, 50-50, 75-25, and 100-0% m/m). Considering the biodegradation rate and the acidification degree, the system with 25% KW had the best performance during the acidogenic phase. When the system was run with 50% KW, it not only had the best stability performance but also had a bigger capacity to treat KW than the system with 25% KW. The system with 50% KW was the best ratio in this two-phase AD system. Co-digestion of KW and FVW by two-phase AD is feasible. The addition of FVW can reduce the inhibition effect caused by salinity and fat concentrations, reduce the HRT, and lead to a higher degree of acidification.

Biogas Recovery from Anaerobic Digestion Process of Mixed Fruit -Vegetable Wastes

Anaerobic digestion of a mix of fruit and vegetable wastes has been carried out in a 200-liter digester within 14 weeks. The wastes were anaerobically digested in an anaerobic digester at ambient temperature. The objective of this paper was to study the performance of the anaerobic process used mixed fruit vegetable wastes as substrates in a single stage fed-batch anaerobic digester for biogas production. The feed consisted of mixed fruit-vegetable wastes were collected from a traditional market in Pontianak city. The wastes were taken based on grab sampling method with a composition of ± 78% vegetable waste, ± 4% tuber waste and ±18% fruit wastes. The total waste weight was 160kg, mixed manually once in the feeding. Chemical analysis of initial waste and bioreactors slurry was performed using standard methods. The COD of the leacheate was in the range of 7.2-56.4g/l, pH in the range of 5.3-6.8 and temperature of 28-46oC. The highest methane content in the biogas was 65% with the biogas flow of 20-40ml/min.

Pilot-scale anaerobic co-digestion of municipal biomass waste: Focusing on biogas production and GHG reduction

Abstract A pilot-scale anaerobic co-digestion research study is presented to elucidate the feasibility of developing anaerobic digestion (AD) as an effective disposal method for municipal biomass waste (MBW) in China, focusing on biogas production and greenhouse gas (GHG) reduction. Food waste, fruit–vegetable waste, and dewatered sewage sludge were co-digested in a continuous stirred-tank reactor for biogas production. Stable operation was achieved with a high biogas production rate of 4.25 m3 (m3 d)−1 at organic loading rate of 6.0 kgVS (m3 d)−1 and hydraulic retention time of 20 d. A total of 16.5% of lipids content was beneficial to the biogas production of the feedstock without inhibition to anaerobic digestion. Compared with the landfill baseline, GHG reduction is an important environmental benefit from MBW digestion. Therefore, anaerobic co-digestion is a promising alternative solution for MBW because it contributes significantly to the sound management of municipal solid waste in China.

Determination of the Effect of Aeration Rate on Composting of Vegetable–Fruit Wastes

AbstractIn this study, it was aimed to determine the effect of various aeration rates on composting to supply the optimum aeration rate for a successful and economic composting. For this aim, vegetable–fruit wastes (VFW) were composted at various aeration rates (0.37, 0.49, 0.62, 0.74, 0.86, and 0.99 L/min kg VS) and moisture, temperature, pH, electrical conductivity, C/N, and cellulose were investigated. Moistures of the reactor that had the highest aeration were generally lower than those of the others. Reactor that had the lowest aeration reached thermophilic phase earlier than the others and stayed more days. This situation was opposite for the reactor that had the highest aeration. pH variations with aeration rates were not significant. Although electrical conductivity did not differ significantly with aeration rates, at the beginning of the thermophilic phase it generally increased with the increase in aeration. The highest C/N reduction was observed in the reactor that had an aeration of 0.62 L/min kg VS. The final cellulose contents were close to each other. It could be said that aeration rates used were efficient on composting of VFW. Taking the C/N into account which is the parameter of the indicator of the stabilization in composting, it could be said that the optimum aeration rate for forced aerobic composting of VFW was 0.62 L/min kg VS.

Biohydrogen from thermophilic co-fermentation of swine manure with fruit and vegetable waste: Maximizing stable production without pH control

Hydrogen production by dark fermentation may suffer of inhibition or instability due to pH deviations from optimality. The co-fermentation of promptly degradable feedstock with alkali-rich materials, such as livestock wastes, may represent a feasible and easy to implement approach to avoid external adjustments of pH. Experiments were designed to investigate the effect of the mixing ratio of fruit–vegetable waste with swine manure with the aim of maximizing biohydrogen production while obtaining process stability through the endogenous alkalinity of manure. Fruit–vegetable/swine manure ratio of 35/65 and HRT of 2 d resulted to give the highest production rate of 3.27 ± 0.51 L H2 L −1 d −1, with a corresponding hydrogen yield of 126 ± 22 mL H2 g −1 VS-added and H 2 content in the biogas of 42 ± 5%. At these operating conditions the process exhibited also one of the highest measured stability, with daily productions deviating for less than 14% from the average.

Semi-continuous co-digestion of solid slaughterhouse waste, manure, and fruit and vegetable waste

The potential of semi-continuous mesophilic anaerobic digestion (AD) for the treatment of solid slaughterhouse waste, fruit-vegetable wastes, and manure in a co-digestion process has been experimentally evaluated. A study was made at laboratory scale using four 2 L reactors working semi-continuously at 35 °C. The effect of the organic loading rate (OLR) was initially examined (using equal proportion of the three components on a volatile solids, VS, basis). Anaerobic co-digestion with OLRs in the range 0.3–1.3 kg VS m −3 d −1 resulted in methane yields of 0.3 m 3 kg −1 VS added, with a methane content in the biogas of 54–56%. However, at a further increased loading, the biogas production decreased and there was a reduction in the methane yield indicating organic overload or insufficient buffering capacity in the digester. In the second part of the investigation, co-digestion was studied in a mixture experiment using 10 different feed compositions. The digestion of mixed substrates was in all cases better than that of the pure substrates, with the exception of the mixture of equal amounts of (VS/VS) solid cattle–swine slaughterhouse waste (SCSSW) with fruit and vegetable waste (FVW). For all other mixtures, the steady-state biogas production for the mixture was in the range 1.1–1.6 L d −1, with a methane content of 50–57% after 60 days of operation. The methane yields were in the range 0.27–0.35 m 3 kg −1 VS added and VS reductions of more than 50% and up to 67% were obtained.

Modelling thermophilic cheese whey bioremediation in a one-stage process

A one-stage bioremediation process for the treatment of cheese whey has been developed, involving use of a mixed population including Bacillus sp. isolated from fruit–vegetable wastes, at elevated temperatures (55, 60, 65 °C), in an aerated system. Based upon a reaction scheme which combined the activities of Lactococcus sp. and thermotolerant yeasts, found in unpasteurised whey, with that of a thermophilic Bacillus sp., we modelled this process using mass balances for a batch culture. We obtained adequate fits to experimental data by simulating the biodegradation of whey components and consequent biomass growth rates using models containing one “lumped” biomass and three “equivalent” substrates (lactose, lactic and acetic acids), with a further simplification of biomass specific growth rate into one constant, “pseudo-exponential” value over the batch. Values of “best fit” model parameters were generated to predict biomass specific growth rates. The average specific growth rate calculated from the models was 0.075 h −1 whilst the experimental one was 0.088 h −1. The results obtained suggest that temperature may be of greater importance to the biodegradation process than dissolved oxygen, as the composition of the microbial community changed with temperature within the range 55–65 °C. High COD removal efficiencies were achieved: up to 93% at 55 °C, and up to 70% at 65 °C. Our investigations suggest that modelling of complex bioreaction systems via “lumping” of key substrates and microbial species into a limited number of “equivalent clusters” is worthy of consideration as a possible means of facilitating rapid process development and practical process operation.