James J. Leahy

Advances in poultry litter disposal technology--a review.

The land disposal of waste from the poultry industry and subsequent environmental implications has stimulated interest into cleaner and more useful disposal options. The review presented here details advances in the three main alternative disposal routes for poultry litter, specifically in the last decade. Results of experimental investigations into the optimisation of composting, anaerobic digestion and direct combustion are summarised. These technologies open up increased opportunities to market the energy and nutrients in poultry litter to agricultural and non-agricultural uses. Common problems experienced by the current technologies are the existence and fate of nitrogen as ammonia, pH and temperature levels, moisture content and the economics of alternative disposal methods. Further advancement of these technologies is currently receiving increased interest, both academically and commercially. However, significant financial incentives are required to attract the agricultural industry.

Characterization of compost produced from separated pig manure and a variety of bulking agents at low initial C/N ratios.

The aim of this study was to investigate the composting of separated pig manure solids with or without a variety of bulking agents at a low initial C/N ratio (12.5-23.3). Compost stability was investigated using an oxygen uptake rate (OUR) test and compost maturity was investigated using a germination index test. All treatments showed typical patterns of compost temperature. Temperatures above 60°C were achieved by Day 2, followed by a thermophilic phase (50-60°C), which lasted for 1 to 2 weeks followed by a cooling phase. The stability of one of treatments which did not contain any bulking agent - OUR of 25 mmol O(2) kg(-1) OM hour(-1) - was negatively affected by its initial high water content (69%). The addition of a bulking agent and initial water content below 60% were necessary to compost the separated solid fraction of pig manure at a low initial C/N ratio.

Pressurised pyrolysis of Miscanthus using a fixed bed reactor.

Miscanthus x giganteus was pyrolysed, in a fixed bed reactor in a constant flow of dinitrogen gas, at a rate of 13°C/min from ambient to 550°C, then held for 25 min at this temperature. The pressures employed ranged from atmospheric to 26 bar. The major compounds identified in the bio-oil were water, phenol, and phenol derivatives. The water contents impact on the usefulness of the bio-oil as a fuel. However, the phenols could provide useful platform chemicals and products. The properties of the char were determined using elemental analyses, surface area measurements using the Brunauer-Emmett-Teller equation, a calorimetric bomb, Scanning Electron Microscopy, and solid state (13)C NMR spectroscopy. The chars were highly carbonised, especially at the higher pressures, and provided thermally stable materials. Pressure impacted greatly on the surface area. Char formed at atmospheric pressure had a surface area of 162 m(2)/g, whereas that from the highest pressure applied was only 0.137 m(2)/g.

Combustion of poultry litter in a fluidised bed combustor

Abstract Combustion studies of poultry litter alone or mixed with peat by 50% on weight basis were undertaken in an atmospheric bubbling fluidised bed. Because of high moisture content of poultry litter, there was some uncertainty whether the combustion could be sustained on 100% poultry litter and as peat is very available in Ireland; its presence was considered to help to improve the combustion. However, the results showed that, as long as the moisture content of poultry litter was kept below 25%, the combustion did not need the addition of peat. The main parameters that were investigated are (i) moisture content, (ii) air staging, and (iii) variations in excess air levels along the freeboard. The main conclusions of the results are (i) combustion was influenced very much by the conditions of the fuel supply, (ii) the steady fuel supply was strongly dependent on the moisture content of the poultry litter, (iii) temperature appeared to be still very influential in reducing the levels of unburned carbon and hydrocarbons released from residues, (iv) the air staging in the freeboard improved combustion efficiency by enhancing the combustion of volatiles released from residues in the riser and (vi) NOx emissions were influenced by air staging in the freeboard. Particles collected from the bed and the two cyclones were analysed to determine the levels of heavy metals and the leachability tests were carried out with ashes collected to verify whether or not they could safely be used in agricultural lands.

Behaviour of meat and bonemeal/peat pellets in a bench scale fluidised bed combustor

As a result of the recent Bovine Spongiform Encephalopathy crisis in the European beef industry, safe animal by-product disposal is currently being addressed. One such disposal option is the combustion of by-product material such as meat and bone meal (MBM) in a fluidised bed combustor (FBC) for the purpose of energy recovery. Two short series of combustion tests were conducted on a FBC (10 cm diameter) at the University of Twente, the Netherlands. In the first series, pellets (10 mm in diameter and approximately 10 mm in length) were made from a mixture of MBM and milled peat, at MBM inclusion rates of 0%, 30%, 50%, 70% and 100%. In the second series of tests, the pellets were commercially made and were 4.8 mm in diameter and between 12 and 15 mm long. These pellets had a weight of about 0.3 g and contained 0%, 25%, 35%, 50% and 100% MBM inclusion with the peat. Both sets of pellets were combusted at 880°C. The residence times in the FBC varied from 300 s (25% MBM inclusion) to 120 s (100% MBM inclusion) for the first series of pellets. Increasing compaction pressure increased the residence time. For the second series of pellets, the residence time varied from about 300 s (25% MBM inclusion) to 100 s (100% MBM inclusion). MBM was found to be a volatile product (about 65%) and co-firing it with milled peat in a pelleted feed format reduces its volatile intensity. Pellets made from 100% bone based meal remained intact within the bed and are thought to have undergone a process of calcination during combustion. A maximum MBM inclusion rate of 35% with milled peat in a pellet is recommended from this work.

Kinetics of levulinic acid and furfural production from Miscanthus × giganteus

This study investigated the kinetics of acid hydrolysis of the cellulose and hemicellulose in Miscanthus to produce levulinic acid and furfural under mild temperature and high acid concentration. Experiments were carried out in an 8L-batch reactor with 9%-wt. biomass loading, acid concentrations between 0.10 and 0.53 M H2SO4, and at temperatures between 150 and 200°C. The concentrations of xylose, glucose, furfural, 5-hydroxymethylfurfural and levulinic acid were used in two mechanistic kinetic models for the prediction of the performance of ideal continuous reactors for the optimisation of levulinic acid and the concurrent production of furfural. A two-stage arrangement was found to maximise furfural in the first reactor (PFR - 185°C, 0.5M H2SO4, 27.3%-mol). A second stage leads to levulinic acid yields between 58% and 72%-mol at temperatures between 160 and 200°C.

Emission and performance characteristics of a 2 litre Toyota diesel van operating on esterified waste cooking oil and mineral diesel fuel

Exhaust emission and performance characteristics were evaluated in a Toyota van, powered by a 2l indirect injection (IDI) naturally aspirated diesel engine, operating on vegetable based waste cooking oil methyl ester (WCOME). Tests were performed on a chassis dynamometer and the data were compared with previous results conducted on the same vehicle using mineral diesel fuel. The data obtained includes smoke opacity, carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), nitrogen dioxide (NO2), nitric oxide (NO), sulfur dioxide (SO2) and brake power. Engine lubricating oil samples were also taken. Results from this study indicated a difference of approximately 9% in brake power between the two fuels. WCOME developed a significant lower smoke opacity level and reduced CO, CO2, SO2 emissions. However, O2, NO2 and NO levels were higher with the vegetable oil based fuel. Power values were comparable for both fuels. Lubricating oil analysis gave little change of viscosity and wear metal concentrations after 2887km were: Silicon 35ppm, Chromium 3.3ppm, Iron 33.8ppm, Copper 14.1ppm and lead 78.6ppm.

Characterisation of the products from pyrolysis of residues after acid hydrolysis of Miscanthus

Platform chemicals such as furfural and hydroxymethylfurfural are major products formed during the acid hydrolysis of lignocellulosic biomass in second generation biorefining processes. Solid hydrolysis residues (HR) can amount to 50 wt.% of the starting biomass materials. Pyrolysis of the HRs gives rise to biochar, bio-liquids, and gases. Time and temperature were variables during the pyrolysis of HRs in a fixed bed tubular reactor, and both parameters have major influences on the amounts and properties of the products. Biochar, with potential for carbon sequestration and soil conditioning, composed about half of the HR pyrolysis product. The amounts (11-20 wt.%) and compositions (up to 77% of phenols in organic fraction) of the bio-liquids formed suggest that these have little value as fuels, but could be sources of phenols, and the gas can have application as a fuel.

Effect of sawdust addition on composting of separated raw and anaerobically digested pig manure

Manures need the addition of carbon-rich bulking agents to conserve N during composting, which increases the cost of the composting process. The recommended proportion of manure/sawdust, based on a carbon (C):nitrogen (N) ratio, is approximately 3:2. Two composting experiments were conducted to determine the impact of varying the proportion of sawdust to either separated raw, or separated anaerobically digested pig manures. To determine stability and maturity of the final compost, oxygen uptake rate (OUR) and germination index (GI) tests were conducted. For both experiments, three treatments were employed: manure-only (Treatment A), manure/sawdust mixed 4:1, fresh weight (Treatment B), and manure/sawdust mixed 3:2, fresh weight (Treatment C). The mixtures were composted in tumblers for 56 days with regular turning. The composting material was tested over the study duration for temperature, pH, water content, organic matter, C:N ratio and bulk density. For both Treatments B and C, the GI indicated low levels of phytotoxicity, and OUR values were lower than the recommended Irish threshold of 13 mmol O(2) kg OM(-1) h(-1), indicating that a high quality compost was produced. The proportion of sawdust to separated manure used can be reduced to make a cost saving, while still producing a stable end-product: 60% less sawdust is required to compost at a manure-to-sawdust ratio of 4:1 compared to the previously recommended ratio of 3:2.

Ruthenium Clusters on Carbon Nanofibers for Formic Acid Decomposition: Effect of Doping the Support with Nitrogen

The catalytic properties of 1 wt % Ru catalysts with the same mean Ru cluster size of 1.4–1.5 nm supported on herringbone‐type carbon nanofibers with different N contents were compared for H2 production from formic acid decomposition. The Ru catalyst on the support with 6.8 wt % N gave a 1.5–2 times higher activity for the dehydrogenation reaction (CO2, H2) than the catalyst on the undoped support. The activity in the dehydration reaction (CO, H2O) was the same. As a result, the selectivity to H2 increased significantly from 83 to 92 % with N‐doping, and the activation energies for both reactions were close (55–58 kJ mol−1). The improvement could be explained by the presence of Ru clusters stabilized by pyridinic N located on the open edges of the external surface of the carbon nanofibers. This N may activate formic acid by the formation of an adduct (>NH+HCOO−) followed by its dehydrogenation on the adjacent Ru clusters.