Methodology to determine the extent of anaerobic digestion, composting and CH4 oxidation in a landfill environment

Abstract: An examination of the processes contributing to the production of landfill greenhouse gas (GHG) emissions is required, as the actual level to which waste degrades anaerobically and aerobically beneath covers has not been differentiated. This paper presents a methodology to distinguish between the rate of anaerobic digestion (rAD), composting (rCOM) and CH4 oxidation (rOX) in a landfill environment, by means of a system of mass balances developed for molecular species (CH4, CO2) and stable carbon isotopes (δ13C-CO2 and δ13C-CH4). The technique was applied at two sampling locations on a sloped area of landfill. Four sampling rounds were performed over an 18 month period after a 1.0 m layer of fresh waste and 30-50 cm of silty clay loam had been placed over the area. Static chambers were used to measure the flux of the molecular and isotope species at the surface and soil gas probes were used to collect gas samples at depths of approximately 0.5, 1.0 and 1.5 m. Mass balances were based on the surface flux and the concentration of the molecular and isotopic species at the deepest sampling depth. The sensitivity of calculated rates was considered by randomly varying stoichiometric and isotopic parameters by ±5% to generate at least 500 calculations of rOX, rAD and rCOM for each location in each sampling round. The resulting average value of rAD and rCOM indicated anaerobic digestion and composting were equally dominant at both locations. Average values of rCOM: ranged from 9.8 to 44.5 g CO2 m-2 d-1 over the four sampling rounds, declining monotonically at one site and rising then falling at the other. Average values of rAD: ranged from 10.6 to 45.3 g CO2 m-2 d-1. Although the highest average rAD value occurred in the initial sampling round, all subsequent rAD values fell between 10 and 20 g CO2 m-2 d-1. rOX had the smallest activity contribution at both sites, with averages ranging from 1.6 to 8.6 g CO2 m-2 d-1. This study has demonstrated that for an interim cover, composting and anaerobic digestion of shallow landfill waste can occur simultaneously

Implementation of a better choice healthy food and drink supply strategy for staff and visitors in government-owned health facilities in Queensland, Australia

Objective The present paper reports on a quality improvement activity examining implementation of A Better Choice Healthy Food and Drink Supply Strategy for Queensland Health Facilities (A Better Choice). A Better Choice is a policy to increase supply and promotion of healthy foods and drinks and decrease supply and promotion of energy-dense, nutrient-poor choices in all food supply areas including food outlets, staff dining rooms, vending machines, tea trolleys, coffee carts, leased premises, catering, fundraising, promotion and advertising. Design An online survey targeted 278 facility managers to collect self-reported quantitative and qualitative data. Telephone interviews were sought concurrently with the twenty-five A Better Choice district contact officers to gather qualitative information. Setting Public sector-owned and -operated health facilities in Queensland, Australia. Subjects One hundred and thirty-four facility managers and twenty-four district contact officers participated with response rates of 48·2 % and 96·0 %, respectively. Results Of facility managers, 78·4 % reported implementation of more than half of the A Better Choice requirements including 24·6 % who reported full strategy implementation. Reported implementation was highest in food outlets, staff dining rooms, tea trolleys, coffee carts, internal catering and drink vending machines. Reported implementation was more problematic in snack vending machines, external catering, leased premises and fundraising. Conclusions Despite methodological challenges, the study suggests that policy approaches to improve the food and drink supply can be implemented successfully in public-sector health facilities, although results can be limited in some areas. A Better Choice may provide a model for improving food supply in other health and workplace settings

Pilot scale evaluation of a model to distinguish the rates of simultaneous anaerobic digestion, composting and methane oxidation in static waste beds

The aim of this paper was to apply and validate a model for measuring the rate and extent of anaerobic digestion, composting and CH4 oxidation in laboratory scale beds. Degradation studies were performed in four reactors each packed with shredded unsorted municipal solid waste, with one bed covered with a 100 mm layer of soil. The rates of production of CH4, CO2, (13)C-CO2 and the rate of consumption of O2 were measured and used as inputs to a mass balance expressions for these components to calculate the rates of anaerobic digestion, composting and CH4 oxidation. The results showed that anaerobic digestion, composting and CH4 oxidation occurred simultaneously in both the covered and uncovered beds. The analysis showed that 50 ± 4% of the solids (COD basis) in the uncovered beds degraded anaerobically, with the generated CH4 subsequently oxidized, and that 32 ± 4% of the solids degraded aerobically in the covered bed

A mass balance model to estimate the rate of composting, methane oxidation and anaerobic digestion in soil covers and shallow waste layers

Although CH oxidation in landfill soil covers is widely studied, the extent of composting and CH oxidation in underlying waste layers has been speculated but not measured. The objective of this study was to develop and validate a mass balance model to estimate the simultaneous rates of anaerobic digestion (r), CH oxidation (r) and composting (r) in environments where O penetration is variable and zones of aerobic and anaerobic activity are intermingled. The modelled domain could include, as an example, a soil cover and the underlying shallow waste to a nominated depth. The proposed model was demonstrated on a blend of biogas from three separate known sources of gas representing the three reaction processes: (i) a bottle of laboratory grade 50:50% CH:CO gas representing anaerobic digestion biogas; (ii) an aerated 250mL bottle containing food waste that represented composting activity; and (iii) an aerated 250mL bottle containing non-degradable graphite granules inoculated with methanotrophs and incubated with CH and O to represent methanotrophic activity. CO, CH, O and the stable isotope C-CO were chosen as the components for the mass balance model. The three reaction rates, r (=r, r, r) were calculated as fitting parameters to the overdetermined set of 4mass balance equations with the net flux of these components from the bottles q (= [Formula: see text] , [Formula: see text] , [Formula: see text] and [Formula: see text] ) as inputs to the model. The coefficient of determination (r) for observed versus modelled values of r were 1.00, 0.97, 0.98 when the stoichiometry of each reaction was based on gas yields measured in the individual bottles and q was calculated by summing yields from the three bottles. r deteriorated to 0.95, 0.96, 0.87 when using an average stoichiometry from 11 incubations of each of the composting and methane oxidation processes. The significant deterioration in the estimation of r showed that this output is highly sensitive to the evaluated stoichiometry coefficients for the reactions. r deteriorated further to 0.86, 0.77, 0.74 when using the average stoichiometry and experimental measurement of the composition and volume of the blended biogas to determine q. This was primarily attributed to average errors of 8%, 7%, 11% and 14% in the measurement of [Formula: see text] , [Formula: see text] , [Formula: see text] and [Formula: see text] relative to the measurement of the same quantities from the individual bottles

A detailed feeding algorithm improves delivery of nutrition support in an intensive care unit

Objective: To determine whether a detailed feeding algorithm improved nutrition support of critically ill patients compared with a standard feeding protocol. Design, setting and participants: Pre-and post-intervention comparison of nutrition commencement and nutritional adequacy in intensive care unit patients receiving enteral or parenteral nutrition until length of stay (LOS) exceeded 30 days, oral intake resumed, the patient was discharged from the ICU or the patient died. The study was conducted at the Royal Brisbane & Women's Hospital, a tertiary hospital with 27 ICU beds, in 2005 (pre-intervention) and 2007 (post-intervention). Intervention: A detailed feeding algorithm that included commencement of nutrition support, progression to goal nutrition rates and management of gastric residual volumes. Main outcome measures: Time to commencement of nutrition support; time to reach goal nutrition rate; nutritional adequacy over ICU stay. Results: No demographic differences between pre-(n = 42) and post-implementation (n = 41) patient groups were observed. Implementation of the detailed feeding algorithm reduced the mean time to commence nutrition support from 28 hours to 16 hours (P=0.035). Time to reach goal nutrition rate fell from 22 hours to 13 hours, although the difference was not statistically significant. There was no significant difference between pre-and post-implementation groups in the number of patients reaching goal volume during ICU admission. Interruptions were a major obstacle to goal volumes of enteral feeds being reached. Conclusions: Introduction of a detailed feeding algorithm resulted in earlier commencement of nutrition support and increased numbers of patients reaching goal rates in less time. To improve nutritional adequacy, the algorithm needs to be modified to account for unavoidable interruptions during ICU stay

A detailed feeding algorithm improves delivery of nutrition support in an intensive care unit

Objective: To determine whether a detailed feeding algorithm improved nutrition support of critically ill patients compared with a standard feeding protocol