Thermophilic anaerobic digestion of food waste

There is a requirement in the European Union to divert organic wastes from landfill because of the risk of methane emissions. One alternative is anaerobic digestion of organic wastes, such as food waste, to stabilise them whilst at the same time recovering the energy from them. One problem with this approach is that the high nitrogen content of food waste may lead to ammonia inhibition. A solution to this has been found for mesophilic digestion but had not been attempted in thermophilic digestion where ammonia toxicity is known to be more acute.The work was carried out in laboratory-scale semi-continuous digesters operated over long time periods to provide maximum opportunity for acclimatisation, and in duplicate to give an indication of reproducibility. A series of experimental runs were undertaken at thermophilic temperatures to assess the influence of trace element (TE) addition on the digestion process. These were carried out at organic loading rates (OLR) of 2, 3 and 4 g volatile solids (VS) l-1 day-1 against unsupplemented controls at OLR 2 g VS l-1 day-1. Although TE addition could offset the accumulation of VFA which occurred in response to an increasing concentration of total ammonical nitrogen (TAN), it could not prevent this. The high alkalinity resulting from ammonia, however, allowed the digesters to continue to produce methane until VFA had accumulated to high concentrations before eventual failure due to a rapid drop in pH.To determine the threshold inhibitory ammonia concentration in thermophilic digestion, one pair of digesters was run on synthetic low nitrogen food waste (low-N food waste) at an OLR 2 g VS l-1 day-1 and compared to a control pair running on domestic food waste at the same loading. All four digesters received TE supplementation. The digesters fed with low-N food waste showed consistently stable performance with pH ~7.4, IA/PA ratio ~0.4-0.5, SMP 0.39 l CH4 g-1 VS, 52-55% CH4, total VFA <500 mg l-1 and 88% VS destruction whereas the controls showed signs of failure after 112 days and irreversible VFA accumulation at a TAN concentration >3.5 g N l-1. One of the low N digesters was supplemented with urea slowly and one by a shock dose: both showed signs of VFA accumulation at TAN >2.5 gl-1 and, again, an irreversible trend in propionic acid build-up when TAN >4 g N l-1. Long term operation showed meta-stable conditions when the digesters were operated at TAN between 2.5 - 3.5g l-1 with oscillations in VFA (especially propionic acid) concentration.Mesophilic digestion at 37oC with TE addition showed very stable performance with pH ~8, IA/PA ? 0.3, SMP ~0.48 l CH4 g-1 VS, 55-60% CH4, total VFA < 300 mg l-1 and VS destruction ~75-78% with a final total ammonia nitrogen (TAN) concentration of 4.5 g N l-1. As the temperature in digesters was raised from 35 to 43 oC in 1oC steps a change in performance was noted when the temperature reached 40 oC. Above this temperature VFA concentrations rose above 4000 mg l-1 and biogas and methane production fluctuated. It is probable that the higher temperature increased the concentration of free ammonia nitrogen (FAN) to ~800 g N l-1 at the measured TAN concentration ~5.5-6.0 g N l-1 and this was sufficient be inhibitory even with TE dosing.Fluorescent in situ hybridisation (FISH) was used to identify the methanogenic populations in some of the trials over selected time periods. This showed changes in population structure both in relation to temperature (mesophilic or thermophilic) and also in response to increasing concentrations of TAN. At high TAN concentrations Methanomicrobiales was the dominant methanogenic group and under mesophilic conditions this proved to be extremely ammonia tolerant. A 14C radio-labelling assay confirmed the dominant pathway to methane formation was by the hydrogenotrophic route which reflected the known metabolic pathway of this methanogen.It was concluded that thermophilic digestion of source segregated domestic food waste would lead to instability and failure of the process unless measures were introduced to reduce the TAN concentration to < 3.5 g N l-1, and preferably to < 2.5 g N l-1.Keywords: Anaerobic digestion, food waste, biogas, VFA accumulation, ammonia inhibition, Fluorescent in situ Hybridisation (FISH

Optimal Application of Swine Effluent in Texas and Oklahoma Panhandles Determined by Bayesian Stochastic Dynamic Programming

A Bayesian stochastic dynamic programming model was used to determine the most efficient time to apply swine effluent to corn production in the Texas and Oklahoma Panhandle area. The total expected ammonia losses when applications were made with and without using weather forecasts were also compared. The monetary values of the weather forecasts were estimated as the cost of additional nitrogen fertilizer to replace the nitrogen lost from nitrogen volatilization. The simulated ammonia loss from the actual hourly weather data showed that 35% of ammonia applied would be lost when the application was made between April 1-5. The expected loss increased to 50% when the application was delayed until May 11-15. The expected nitrogen loss was reduced to 25% when the producer made an application only upon receiving a favorable weather forecast and was willing to operate the pivot for a six-hour period either day or night. If the producer applied effluent on a 12-hour day time only schedule but applied only after receiving a favorable forecast, the expected loss declined from 35 % to 30%. With nitrogen at 0.50 per pound, the value of the forecast information for a 128 acre corn field was 780 and 430 for the six-hour application and twelve-hour daytime-only application methods, respectively. There was a benefit of 463 for the 128-acre corn field from applying the effluent on a flexible six-hour day and/or night method as opposed to the 12-hour daytime only schedule.Department of Agricultural Economic

Optimal Application of Swine Effluent under Stochastic Weather Conditions in the Texas and Oklahoma Panhandles

Ammonia Volatilization, Animal Waste, Irrigation, Swine Effluent, Target MOTAD, Production Economics, Resource /Energy Economics and Policy,

An Optimal Application of Swine Effluent in Texas and Oklahoma Panhandle Determined by Bayesian Stochastic Dynamic Programming

Swine Effluent Irrigation, Environmental Economics and Policy,

The Development of Performance Appraisal Model of First Line Management in Thai Foundry Industry

The quality research purpose were 1) to investigate work roles and responsibilities, which are elements of the performance appraisal model of first line managements in Thai foundry industry, 2) to development the performance appraisal model of first line managements in Thai foundry industry, and 3) to development the performance appraisal manual of first line managements in Thai foundry industry. The participants were a first line management in the production line in a medium Thai foundry industry from 37 companies. The statistics used in the research included percentage, standard deviation, consistency index, and the content validity index. The research result revealed the following. 1) Work roles and responsibilities as the components of the performance appraisal model of first line managements in Thai foundry industry. It was found that had two key functions and nine units of competence. The nine elements of competence were divided into 3 levels (1) practitioner head level 13 jobs, (2) supervisor head level 21 jobs, and (3) professional skilled level 15 jobs. 2) The performance appraisal model of first line managements in Thai foundry industry obtained from the discussion hearing demonstrated six stages of the development and after the model was evaluated and developed by the experts, it was found that the model was in the highest level. 3) The performance appraisal manual of first line managements in Thai foundry industry form consisted of knowledge assessment, skill assessment, and behavioral assessment. After the performance appraisal manual was evaluated (content validity index) by the experts, it was found that the manual was in 1.00 level. And the performance appraisal manual obtained was applied with six samples and some were under 80% of the performance benchmark and had to enroll into individual development plan for catching up with the organization standard on the knowledge and skills

Antibodies Among Healthy Population of Developing Countries Against Enterohaemorrhagic Escherichia coli O157:H7

In Thailand, no reports are available on Escherichia coli serotype O157:H7, a causative agent of severe bloody diarrhoea, sometimes associated with haemolytic-uraemic syndrome and thrombotic thrombo-cytopenic purpura. The reason for the non-identification of infection due to E. coli O157 in this country and in other developing countries has not been rigorously discussed. The aim of this study was to determine the humoral response against the infectious organism. The IgM and IgG antibody responses against E. coli O157 lipopolysaccharide were studied using indirect enzyme-linked immunosorbent assay. Three hundred and thirty-two serum samples obtained from healthy blood donors and patients with diseases unrelated to diarrhoea were investigated. With a cut-off value of mean +2 SDs for each age-group, the frequency of the IgM and IgG responses to O157 lipopolysaccharide was 11.74% (39 of 332 samples) and 22.59% (75 of 332 samples) respectively. Furthermore, agglutination test of 173 subjects revealed titres ranging from 10 to 40 in all the samples. The results suggest possible exposure of the Thai population to cross-reacting antigens from other intestinal organisms in addition to infection due to E. coli O157:H7

Bamboo as a Sustainable Building Material—Culm Characteristics and Properties

Bamboo culm is a renewable and lightweight material with high strength, particularly tensile strength. It is well accepted that bamboo culms have played a significant role in architecture because of their sustainable contribution. The culm characteristics and properties of three-year-old bamboo from five species (Dendrocalamus asper, Dendrocalamus sericeus, Dendrocalamus membranaceus, Thyrsostachys oliveri, and Phyllostachys makinoi) were investigated. The results show that each bamboo species has different culm characteristics along with culm length. Culm size, particularly the outer culm diameter and culm wall thickness, affects the ultimate load. These results confirm that a bigger culm with a thicker wall could receive more load. D. asper received the highest ultimate load, while T. oliveri received the lowest ultimate load. However, when calculating the test results for stress (load per cross-section area), P. Makinoi showed excellent mechanical properties, while D. asper showed the worst mechanical properties. This research promotes bamboo’s appropriate use for building applications and as a more sustainable material for architecture

Determinants of Farm Decision to Enter Land Diversion: The Case of Upland Farmers in Northern Thailand

Mixed cropping has advantages to famers because it allows diversification for reducing risk, which caused by unfavorable weather and market price variability. This research aims to analyze and determine factors that influence farmer’s decision to transfer from growing traditional crops (a single crop such as corn and lychee) to diversified crops. The logit model was used to identify factors associated with the farmer’s decision. Models based on a face-face survey of 185 respondents from six villages in Lampang province belonging to the highland community of northern Thailand. The results showed that farmer’ decision to enter into land diversion was different in terms of farmers’ socio-economic factor such as the education level of the farmer and household debt. The government subsidy and technical assistance of the agricultural extension services also significantly influent the farmer’s decision to accept the crop diversified method

Influence of ammonia in the anaerobic digestion of food waste

Ammonia toxicity was investigated in mesophilic (37 °C) and thermophilic (55 °C) digesters using high and lownitrogen food wastes (FW). Mesophilic inoculum was successfully acclimated to thermophilic conditions by a step change in temperature followed by incremental increases in organic loading rate (OLR). Digestion performance and stability were monitored via volatile fatty acid (VFA) profiles, alkalinity, specific methane production (SMP) and volatile solids (VS) destruction. High-nitrogen mesophilic digesters stabilised by day 70 and responded well to increases in OLR, with a SMP of 0.45 L CH4 g−1 VS, stable pH, and VFA<0.2 g L−1. Thermophilic digesters fed on high and low-nitrogen FWs showed almost identical responses to acclimatisation. Behaviour then deviated, with high-nitrogen digesters accumulating VFA. Stable pH could be maintained for up to 310 days before eventual failure at total ammonia nitrogen (TAN) concentration>5.0 g N L−1, although accumulation of propionic and other longer-chain VFA began at TAN ∼3.5 g N L−1. The low-nitrogen digesters showed no VFA accumulation, and had a SMP of ∼0.39 L CH4 g VS L−1 day−1 with 91% VS destruction. After 384 days the TAN concentration was increased from ∼0.7 g N L−1 by urea addition. This resulted in progressive VFA accumulation in one digester when TAN reached ∼3.5 g N L−1, while stable operation at very low VFA was possible at up to ∼2.5 g N L−1 in the second digester. The results confirmed acclimatisation to thermophilic conditions was possible on a far shorter timescale than to high TAN concentrations

The Determinants of Farmers� Cropping Systems Adoption: A Case of the Upland Farmers in Northern Thailand

Lack of farming knowledge still appears in the remote areas of northern Thailand particularly among upland farmers who often use conventional farming and mono-cropping techniques. The cropping system involves a specialization skill in production from farmers and it does require a large quantity of land to meet and individual farmer’s need. Over the past decade, the forest cover in northern Thailand had dramatically decreased due to demands of land cultivation. As a multi-cropping system may provide advantages to the farmers, intercropping and sequential cropping system can help to minimize crop production and price risks. The system does not only give sufficient economic returns but it also provides a long-term ecological sustainability. This practice is a way to transform upland farmers into becoming more self-reliant. This research aimed to analyze and determine the key factors of farmers’ decision to adopt the multi-cropping practice. Logit model was applied in the study, and was based on a survey of 202 respondents from the highland communities of northern Thailand. The results showed that the famers’ education attainment, attitude toward environmental awareness, and household financial situation are important to their choice of practicing the multi-cropping system. Education and lower debt amount led to an increase in the probability of upland farmers to try the multi-cropping system. The households with larger farms are willing to use part of their available land to do the multi-cropping. An increase in the farmers’ level of environmental concern was also observed to increase the probability of the multi-cropping system being adopted