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Anaerobic gas production tests, generically Biochemical Methane Potential (BMP) or Biogas Potential (BP) tests, are often used to assess biodegradability, though long duration limits their utility. This research investigated whether simple modelling approaches could provide a reliable earlier prediction of total biogas production. Data were assessed from a non-automated biogas test on a large number of both fresh and processed municipal solid waste (MSW) samples, sourced from a mechanical biological treatment (MBT) plant. Non-linear models of biogas production curves were useful in identifying a suitable test endpoint, supporting a test duration of 50 days. Biogas production at 50 days (B50) was predicted using the first 14 days of test data, using (a) linear correlation, (b) a new linearisation process, and (c) non-linear kinetic models. Prediction errors were quantified as relative root mean squared error of prediction (rRMSEP), and bias. Predictions from most models were improved by removing the initial exponential increase phase. Linear correlation gave the most precise and accurate predictions at 14 days (rRMSEP = 2.8%, bias under 0.05%) and allowed acceptable prediction (rRMSEP <10%) both at 8 days, and at 6 days using separate correlations for each sample type. Of the other predictions, the new linearisation process gave the lowest rRMSEP (10.6%) at 14 days. More complex non-linear models conferred no advantage in prediction of B50. These results demonstrate that early prediction of anaerobic gas production is possible for a well-optimised test, using only basic equipment and without recourse to external data sources or complex mathematical modelling.
Graham Howell; Chris Bennett; Dušan Materić. A comparison of methods for early prediction of anaerobic biogas potential on biologically treated municipal solid waste. Journal of Environmental Management 2018, 232, 887 -894.
AMA StyleGraham Howell, Chris Bennett, Dušan Materić. A comparison of methods for early prediction of anaerobic biogas potential on biologically treated municipal solid waste. Journal of Environmental Management. 2018; 232 ():887-894.
Chicago/Turabian StyleGraham Howell; Chris Bennett; Dušan Materić. 2018. "A comparison of methods for early prediction of anaerobic biogas potential on biologically treated municipal solid waste." Journal of Environmental Management 232, no. : 887-894.
The ORG0020 dynamic respiration test is effective at distinguishing source segregated organic waste derived composts across a wide range of stabilities when compared to other standard tests; however, using the original diaphragm pump and manifold setup, the test is affected by variability in flow rate with time and across sample replicate vessels. Here, we demonstrate the use of a multichannel peristaltic pump to deliver a more consistent air flow to individual vessels. Using finished and unfinished industry compost samples from different sites with varying stabilities, we provide evidence of greater precision of the modified setup compared to the original. Furthermore, the reduced need for air flow adjustment resulted in improved running cost efficiency with less labour demand. Analysis of compost sample oxygen demand supports the current test air flow rate of 25–75 mL min−1, although the improved air flow control will enable future narrowing of the acceptable range for better inter-laboratory performance.
Diana Guillen Ferrari; Graham Howell; Thomas J. Aspray. Improved Precision and Efficiency of a Modified ORG0020 Dynamic Respiration Test Setup for Compost Stability Assessment. Sustainability 2017, 9, 2358 .
AMA StyleDiana Guillen Ferrari, Graham Howell, Thomas J. Aspray. Improved Precision and Efficiency of a Modified ORG0020 Dynamic Respiration Test Setup for Compost Stability Assessment. Sustainability. 2017; 9 (12):2358.
Chicago/Turabian StyleDiana Guillen Ferrari; Graham Howell; Thomas J. Aspray. 2017. "Improved Precision and Efficiency of a Modified ORG0020 Dynamic Respiration Test Setup for Compost Stability Assessment." Sustainability 9, no. 12: 2358.
The purpose of this work was to evaluate compost (and related industry) stability tests given recent large-scale changes to feedstock, processing techniques and compost market requirements. Five stability tests (ORG0020, DR4, Dewar self-heating, oxygen update rate (OUR) and static respiration) were evaluated on composts from ten in-vessel composting sites. Spearman rank correlation coefficients were strong for the ORG0020, OUR and DR4 (both CO2 and O2 measurement), however, OUR results required data extrapolation for highly active compost samples. By comparison the Dewar self-heating and static respiration tests had weaker correlations, in part the result of under reporting highly active, low pH samples. The findings suggest that despite differences in pre-incubation period both dynamic respiration tests (ORG0020 and DR4) are best suited to deal with the wide range of compost stabilities found.
Thomas J. Aspray; Mary E. Dimambro; Phil Wallace; Graham Howell; James Frederickson. Static, dynamic and inoculum augmented respiration based test assessment for determining in-vessel compost stability. Waste Management 2015, 42, 3 -9.
AMA StyleThomas J. Aspray, Mary E. Dimambro, Phil Wallace, Graham Howell, James Frederickson. Static, dynamic and inoculum augmented respiration based test assessment for determining in-vessel compost stability. Waste Management. 2015; 42 ():3-9.
Chicago/Turabian StyleThomas J. Aspray; Mary E. Dimambro; Phil Wallace; Graham Howell; James Frederickson. 2015. "Static, dynamic and inoculum augmented respiration based test assessment for determining in-vessel compost stability." Waste Management 42, no. : 3-9.
[1] Sulfate in acid rain is known to suppress methane (CH4) emissions from natural freshwater wetlands. Here we examine the possibility that CH4 emissions from rice agriculture may be similarly affected by acid rain, a major and increasing pollution problem in Asia. Our findings suggest that acid rain rates of SO42− deposition may help to reduce CH4 emissions from rice agriculture. Emissions from rice plants treated with simulated acid rain at levels of SO42− consistent with the range of deposition in Asia were reduced by 24% during the grain filling and ripening stage of the rice season which accounts for 50% of the overall CH4 that is normally emitted in a rice season. A single application of SO42− at a comparable level reduced CH4 emission by 43%. We hypothesize that the reduction in CH4 emission may be due to a combination of effects. The first mechanism is that the low rates of SO42− may be sufficient to boost yields of rice and, in so doing, may cause a reduction in root exudates to the rhizosphere, a key substrate source for methanogenesis. Decreasing a major substrate source for methanogens is also likely to intensify competition with sulfate‐reducing microorganisms for whom prior SO42− limitation had been lifted by the simulated acid rain S deposition.
Vincent Gauci; Nancy B. Dise; Graham Howell; Meaghan E. Jenkins. Suppression of rice methane emission by sulfate deposition in simulated acid rain. Journal of Geophysical Research 2008, 113, 1 .
AMA StyleVincent Gauci, Nancy B. Dise, Graham Howell, Meaghan E. Jenkins. Suppression of rice methane emission by sulfate deposition in simulated acid rain. Journal of Geophysical Research. 2008; 113 ():1.
Chicago/Turabian StyleVincent Gauci; Nancy B. Dise; Graham Howell; Meaghan E. Jenkins. 2008. "Suppression of rice methane emission by sulfate deposition in simulated acid rain." Journal of Geophysical Research 113, no. : 1.
Jim Frederickson; Graham Howell; Andrew M. Hobson. Effect of pre-composting and vermicomposting on compost characteristics. European Journal of Soil Biology 2007, 43, S320 -S326.
AMA StyleJim Frederickson, Graham Howell, Andrew M. Hobson. Effect of pre-composting and vermicomposting on compost characteristics. European Journal of Soil Biology. 2007; 43 ():S320-S326.
Chicago/Turabian StyleJim Frederickson; Graham Howell; Andrew M. Hobson. 2007. "Effect of pre-composting and vermicomposting on compost characteristics." European Journal of Soil Biology 43, no. : S320-S326.
Summary A large-scale, outdoor vermicomposting system was monitored for 80 weeks. Earthworm populations were recorded for 60 weeks in unheated beds operating at ambient temperatures (34 weeks at 6.3 ± 2.3 °C) and in heated beds controlled at 13.7 ± 0.8 °C for 34 weeks. Both blocks of beds were at ambient temperatures for the remaining 26 weeks. Earthworm biomass and the numbers of hatchlings and cocoons produced for the heated beds were found to be significantly greater than for the unheated beds. Nitrous oxide fluxes in winter (week 60) were 3.2 ± 0.3 mg m –2 h –1 (unheated beds), 1.8 ± 0.3 mg m –2 h –1 (heated beds), and these were significantly different to the control beds (0.1 ± 0.0 mg m –2 h –1 ). Emissions during summer (week 80) were 20.1 ± 3.0 mg m –2 h –1 (unheated beds), 21.3 ± 2.8 mg m –2 h –1 (heated beds) and these were significantly different to the control beds 3.9 ± 1.7 mg m –2 h –1 . No relationship between earthworm density and nitrous oxide flux was found for the large-scale beds. However, in a subsequent laboratory experiment, nitrous oxide emissions were positively correlated with earthworm density (R 2 = 0.76). Maintaining moderate bed temperatures for vermicomposting systems during low ambient temperatures can significantly increase earthworm density. Vermicomposting systems have the capacity to emit high levels of nitrous oxide and earthworms appear to be primarily responsible for this. The environmental impact from nitrous oxide emissions appears to be comparable to other waste processing operations. Further research is required into ways of minimising emissions especially from vermicomposting systems operating at high earthworm densities and high waste processing rates.
James Frederickson; Graham Howell. Large-scale vermicomposting: emission of nitrous oxide and effects of temperature on earthworm populations: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002. Pedobiologia 2003, 47, 724 -730.
AMA StyleJames Frederickson, Graham Howell. Large-scale vermicomposting: emission of nitrous oxide and effects of temperature on earthworm populations: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002. Pedobiologia. 2003; 47 (5):724-730.
Chicago/Turabian StyleJames Frederickson; Graham Howell. 2003. "Large-scale vermicomposting: emission of nitrous oxide and effects of temperature on earthworm populations: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002." Pedobiologia 47, no. 5: 724-730.