Environmental assessment of landfill gas mitigation using biocover and gas collection with energy utilisation at aging landfills.

A life cycle-based environmental assessment was conducted on the mitigation of landfill gas emissions, by implementing biocover and gas collection along with energy utilisation at aging landfills. Based on recent studies about gas generation at Danish landfills, the efficiency of the mitigation technologies involved and the composition of substituted energy production, 15 scenarios were modelled using the EASETECH life cycle assessment model, through which potential environmental impacts in the category "Climate change" were calculated. In all scenarios, biocover and gas collection systems with energy utilisation led to significant environmental improvements compared to the baseline scenario with no emission mitigation action. Scenarios representing biocovers with methane oxidation efficiencies between 70 and 90 % were environmentally superior in terms of climate change impact - in comparison to scenarios with 20-30 years of gas collection and energy utilisation (collection efficiencies between 40 and 80 %). Combining gas collection with energy utilisation and the subsequent installation of a biocover saw major improvements in comparison to where only gas collection and energy utilisation were in effect. Overall, it can be concluded that a biocover under the given assumptions is environmentally more appropriate than gas collection and utilisation at aging landfills, mainly due to methane emissions escaping through the landfill cover during and after the gas collection period playing a crucial role in the latter situation. Maintaining high methane oxidation efficiency for a biocover throughout the lifetime of a landfill is vital for reducing environmental impacts.

The effect of barometric pressure changes on the performance of a passive biocover system, Skellingsted landfill, Denmark.

This study investigated the performance of a passive biocover system at a Danish landfill. The overall methane oxidation efficiency of the system was assessed by comparing annual whole-site methane emissions before and after biocover installation. Annual whole-site methane emission predictions were calculated based on empirical models developed by a discrete number of tracer gas dispersion measurements. Moreover, a series of field campaigns and continuous flux measurements was carried out to evaluate the functionality of an individual biowindow. The results indicated that biocover system performance highly depended on barometric pressure variations. Under decreasing barometric pressure, estimated efficiency declined to 20%, while under increasing barometric pressure, nearly 100% oxidation was achieved. In-situ measurements on a specific biowindow showed a similar oxidation efficiency pattern in respect to barometric pressure changes despite the difference in spatial representation. Eddy covariance results revealed pronounced seasonal variability in the investigated biowindow, measuring higher methane fluxes during the cold period compared to the warm period. Results from the in-situ campaigns confirmed this finding, reporting a threefold increase in the biowindow's methane oxidation capacity from April to May. The annual average oxidation efficiency of the system was estimated to range between 51% and 65%, taking into consideration the impact of changes in barometric pressure and seasonal variability. This indicated an annual reduction in landfill's methane emissions between 24 and 35 tonnes. This study revealed the challenge facing current approaches in documenting accurately the performance of a passive biocover system, due to the short-term variability of oxidation efficiency, which is influenced by barometric pressure changes.

Annual upscaling of methane emission field measurements from two Danish landfills, using empirical emission models.

An empirical model was developed and employed to estimate annual methane (CH4) emissions from two Danish landfills (Skellingsted and AV Miljø). The overall aim was to provide accurate annual CH4 emission estimates based on discrete emission field measurements and to address temporal variability caused by the impact of barometric pressure. Four non-linear regression models were developed, corresponding to the two landfills as well as to the western and eastern waste sections of AV Miljø. A comparison of model predictions with on-site eddy covariance fluxes showed that the models can accurately predict short-term emission variability. Predicted annual CH4 emissions for the Skellingsted and AV Miljø landfills were 69 ± 4 and 80 ± 4 tonnes, respectively, whereas for the western and eastern sections of the AV Miljø landfill, emissions were estimated at 63 ± 3 and 19 ± 1 tonnes, respectively. The results demonstrate that even though maximum emissions from Skellingsted were approximately threefold compared to AV Miljø, annual predicted CH4 emissions for Skellingsted were lower. This was because during the most frequently occurring pressure change events, emission rates were higher at AV Miljø in comparison to Skellingsted. An optimised sampling strategy was proposed, targeting the determination of an empirical emission model though the effective use of discrete field measurements. Analysis of annual emission estimates, based on the number of the tracer dispersion method (TDM) measurements, showed that both the number as well as the distribution of performed TDM measurements across the range of expected dP/dt influence the uncertainty.

Revisiting the passive biocover system at Klintholm landfill, six years after construction.

A biocover system was established at Klintholm landfill in Denmark in 2009 to mitigate methane emissions, and the system exhibited high mitigation efficiency during the first year after implementation. The biocover system was revisited in 2016/2017, and a series of field and laboratory tests were carried out to evaluate functionality about six years after establishment. Three field campaigns were executed in three different barometric pressure conditions, namely increasing, stable and decreasing. Local surface flux measurements and gas concentration profiles in the methane oxidation layer showed that barometric pressure changes had a significant effect on gas emission and methane oxidation. Elevated concentrations of oxygen were observed in the gas distribution layer, and field data showed that significant methane oxidation took place in this location. This finding was verified in laboratory-based methane oxidation incubation tests. Temperatures higher than ambient temperature were observed throughout the methane oxidation layer, with average temperatures ranging between 13 and 27 °C, even in the coldest month of the year. Field measurements showed that total methane emissions from the whole landfill cell were at the same level or lower than measurements performed in 2009/2010 after implementation of the biocover system, and laboratory tests showed methane oxidation potential approximately equal to former tests. In spite of an inhomogeneous distribution of landfill gas load to the methane oxidation layer, the performance of the biocover system had not declined over the 6-7 years since its establishment, even though no maintenance had been carried out in the intervening years.

Methane emissions from Icelandic landfills - A comparison between measured and modelled emissions.

This study compares methane (CH4) emissions from five Icelandic landfills, quantified using tracer gas dispersion to modelled emission rates using the IPCC FOD model. The average CH4 emission rates measured from the investigated landfills were 475.4 kg CH4 h-1 (Álfsnes landfill), 32.5 kg CH4 h-1 (Fíflholt), 40.8 kg CH4 h-1 (Gufunes), 9.8 kg CH4 h-1 (Kirkjuferjuhjáleiga) and 78.4 kg CH4 h-1 (Stekkjarvík). At three of the landfills (Álfsnes, Fíflholt and Kirkjuferjuhjáleiga), the modelled emission was higher than the measured emission by factors ranging from 1.1 to 4.8, neglecting any CH4 oxidation in the cover soils. Even though CH4 oxidation might play a role at some of the investigated landfills, and thus reduce the gap between modelled and measured emissions, it is likely that the model overestimated CH4 generation due to uncertainties in input model parameters. Assuming that the measured emissions at the five landfills are representative of all the waste disposed in Iceland from 2007 to 2016, the measured emission should be extrapolated to 817 kg CH4 h-1, which is relatively close to the modelled national emission of 936 kg CH4 h-1 in 2017. This study showed that the application of the IPCC FOD model at national level is appropriate for estimating landfill CH4 emissions in Iceland. CH4 emissions from landfills in Iceland can be reduced by expanding or implementing gas collection or biocover systems for optimised microbial oxidation.

Methane emission dynamics from a Danish landfill: The effect of changes in barometric pressure.

This study investigates temporal variability on landfill methane (CH4) emissions from an old abandoned Danish landfill, caused by the rate of changes in barometric pressure. Two different emission quantification techniques, namely the dynamic tracer dispersion method (TDM) and the eddy covariance method (EC), were applied simultaneously and their results compared. The results showed a large spatial and temporal CH4 emission variation ranging from 0 to 100 kg h-1 and 0 to 12 µmol m-2 s-1, respectively. Landfill CH4 emissions dynamics were influenced by two environmental factors: the rate of change in barometric pressure (a strong negative correlation) and wind speed (a weak positive correlation). The relationship between CH4 emissions and the rate of change in barometric pressure was more complicated than a linear one, thereby making it difficult to estimate accurately annual CH4 emissions from a landfill based on discrete measurements. Furthermore, the results did not show any clear relationship between CH4 emissions and ambient temperature. Large seasonal variations were identified by the two methods, whereas no diurnal variability was observed throughout the investigated period. CH4 fluxes measured with the EC method were strongly correlated with emissions from the TDM method, even though no direct relationship could be established, due to the different sampling ranges of the two methods and the spatial heterogeneity of CH4 emissions.

Closing the methane mass balance for an old closed Danish landfill.

In this study, a methane (CH4) mass balance was established for Hedeland landfill. CH4 generation rates were modelled using a multiphase first-order decay model (The Afvalzorg model) and determined at between 57 and 79 kg h-1. The CH4 emission rate was quantified at between 2 and 14 kg h-1, using the tracer gas dispersion method and the CH4 gas recovery efficiency was between 8 and 21%. At three places along the perimeter of the landfill, gas remediation systems have been installed to protect the residential houses from any risk of migrating landfill gas. About 0.76 kg h-1 of CH4 was extracted from these three remediation systems. Using a carbon mass balance for the lateral migrating landfill gas showed a fractional oxidation of about 78%, which corresponded to a CH4 flux of 3.5 kg h-1 from the three remediation systems, including the oxidised CH4. The total lateral CH4 flux (un-oxidised) from the total landfill perimeter was estimated at between 6.9 and 10.4 kg h-1. CH4 oxidation efficiency in the landfill cover soil, determined from stable carbon isotope analyses, was found to be between 12% and 92%. This resulted in an average CH4 oxidation rate of 32 kg h-1, using an average CH4 emission rate of 8 kg h-1. CH4 surface screenings and surface flux measurements supported the hypothesis that oxidation efficiency was in the higher range and that oxidation could close the CH4 mass balance.

Biofiltration of diluted landfill gas in an active loaded open-bed compost filter.

Microbial oxidation in a biofilter is a treatment solution for diluted landfill gas (LFG), for instance at old landfills, where LFG recovery is no longer feasible, or from remediation systems designed to cut off laterally migrating LFG. In this study, an actively loaded open-bed compost filter, designed for the treatment of diluted LFG, was tested at an old landfill in Denmark. An 18 m3 biofilter was constructed in a 30 m3 container loaded with LFG mixed with air, in order to obtain diluted LFG. The inlet concentration of methane (CH4) fluctuated between 4.4 and 9.2 vol% during the five tested flow campaigns, resulting in CH4 loads of 106-794 g CH4 m-2 d-1. The maximum identified CH4 oxidation rate was 460 g m-2 d-1, with an overall CH4 oxidation efficiency of 58%. Due to preferential flows, especially along the edges of the filter at the transition points between the compost and the container wall, an overall CH4 oxidation efficiency of 100% was never achieved. However, pore gas profiles in selected areas in the filter material showed oxidation efficiencies close to 100%. The results were supported by tracer gas tests showing average oxidation efficiency in the nine measuring points of 89% at a CH4 load of 487 ± 64 g CH4 m-2 d-1.

Measuring methane emissions from a UK landfill using the tracer dispersion method and the influence of operational and environmental factors.

The methane emissions from a landfill in south-east, UK were successfully quantified during a six-day measurement campaign using the tracer dispersion method. The fair weather conditions made it necessary to perform measurements in the late afternoon and in the evening when the lower solar flux resulted in a more stable troposphere with a lower inversion layer. This caused a slower mixing of the gasses, but allowed plume measurements up to 6700 m downwind from the landfill. The average methane emission varied between 217 ±â€¯14 and 410 ±â€¯18 kg h-1 within the individual measurement days, but the measured emission rates were higher on the first three days (333 ±â€¯27, 371 ±â€¯42 and 410 ±â€¯18 kg h-1) compared to the last three days (217 ±â€¯14, 249 ±â€¯20 and 263 ±â€¯22 kg h-1). It was not possible to completely isolate the extent to which these variations were a consequence of measuring artefacts, such as wind/measurement direction and measurement distance, or from an actual change in the fugitive emission. Such emission change is known to occur with changes in the atmospheric pressure. The higher emissions measured during the first three days of the campaign were measured during a period with an overall decrease in atmospheric pressure (from approximately 1014 mbar on day 1 to 987 mbar on day 6). The lower emissions measured during the last three days of the campaign were carried out during a period with an initial pressure increase followed by a period of slowly reducing pressure. The average daily methane recovery flow varied between 633 and 679 kg h-1 at STP (1 atm, 0 °C). The methane emitted to the atmosphere accounted for approximately 31% of the total methane generated, assuming that the methane generated is the sum of the methane recovered and the methane emitted to the atmosphere, thus not including a potential methane oxidation in the landfill cover soil.

AERMOD as a Gaussian dispersion model for planning tracer gas dispersion tests for landfill methane emission quantification.

The measurement of methane emissions from landfills is important to the understanding of landfills' contribution to greenhouse gas emissions. The Tracer Dispersion Method (TDM) is becoming widely accepted as a technique, which allows landfill emissions to be quantified accurately provided that measurements are taken where the plumes of a released tracer-gas and landfill-gas are well-mixed. However, the distance at which full mixing of the gases occurs is generally unknown prior to any experimental campaign. To overcome this problem the present paper demonstrates that, for any specific TDM application, a simple Gaussian dispersion model (AERMOD) can be run beforehand to help determine the distance from the source at which full mixing conditions occur, and the likely associated measurement errors. An AERMOD model was created to simulate a series of TDM trials carried out at a UK landfill, and was benchmarked against the experimental data obtained. The model was used to investigate the impact of different factors (e.g. tracer cylinder placements, wind directions, atmospheric stability parameters) on TDM results to identify appropriate experimental set ups for different conditions. The contribution of incomplete vertical mixing of tracer and landfill gas on TDM measurement error was explored using the model. It was observed that full mixing conditions at ground level do not imply full mixing over the entire plume height. However, when full mixing conditions were satisfied at ground level, then the error introduced by variations in mixing higher up were always less than 10%.

Assessment of a landfill methane emission screening method using an unmanned aerial vehicle mounted thermal infrared camera - A field study.

An unmanned aerial vehicle (UAV)-mounted thermal infrared (TIR) camera's ability to delineate landfill gas (LFG) emission hotspots was evaluated in a field test at two Danish landfills (Hedeland landfill and Audebo landfill). At both sites, a test area of 100 m2 was established and divided into about 100 measuring points. The relationship between LFG emissions and soil surface temperatures were investigated through four to five measuring campaigns, in order to cover different atmospheric conditions along with increasing, decreasing and stable barometric pressure. For each measuring campaign, a TIR image of the test area was obtained followed by the measurement of methane (CH4) and carbon dioxide (CO2) emissions at each measuring point, using a static flux chamber. At the same time, soil temperatures measured on the surface, at 5 cm and 10 cm depths, were registered. At the Hedeland landfill, no relationship was found between LFG emissions and surface temperatures. In addition, CH4 emissions were very limited, on average 0.92-4.52 g CH4 m-2 d-1, and only measureable on the two days with decreasing barometric pressure. TIR images from Hedeland did not show any significant temperature differences in the test area. At the Audebo landfill, an area with slightly higher surface temperatures was found in the TIR images, and the same pattern with slightly higher temperatures was found at a depth of 10 cm. The main LFG emissions were found in the area with the higher surface temperatures. LFG emissions at Audebo were influenced significantly by changes in barometric pressure, and the average CH4 emissions varied between 111 g m-2 d-1 and 314 g m-2 d-1, depending on whether the barometric pressure gradient had increased or decreased, respectively. The temperature differences observed in the TIR images from both landfills were limited to between 0.7 °C and 1.2 °C. The minimum observable CH4 emission for the TIR camera to identify an emission hotspot was 150 g CH4 m-2 d-1 from an area of more than 1 m2.

Regulating landfills using measured methane emissions: An English perspective.

Methane emissions from landfills are an important source of greenhouse gases in the UK and worldwide. This paper considers how measurements of methane emissions could be used to regulate landfills in England in order to reduce the contribution of landfilling to climate change. The paper presents the results of a number of UK studies undertaken to quantify methane emissions from landfills. The methods used have included the DIAL (Differential Absorption Lidar) technique and a tracer gas dispersion method. A method based on aerial measurements has been developed. Methane emission rates were measured at 15 biodegradable waste landfills. All of the landfills where measurements took place had an active landfill gas extraction system. A methane collection index (MCI) is calculated for each landfill using the ratio of the methane collection rate to the sum of the collection and emission rates. The values of the index in the campaigns reported here ranged from 0.28 to 0.90. The modern operational landfills surveyed achieved MCI values with a much narrower range of between 0.64 and 0.90 with an average of 0.76. This has demonstrated that it is possible for these landfills to collect a high proportion of the landfill gas. A proposed approach is presented for regulating landfills using the measured MCI. This would involve an annual measurement campaign to quantify the methane emissions and the use of the data provided by these surveys to develop an achievable but challenging MCI limit. A limit value of 0.75 for the MCI is used to illustrate the approach. An MCI that falls below the limit would trigger actions to reduce the methane emissions from the landfill.

Validation and error assessment of the mobile tracer gas dispersion method for measurement of fugitive emissions from area sources.

A controlled release test was carried out to assess the accuracy of the tracer gas dispersion method, which is used to measure whole-site landfill methane (CH4) emissions as well as fugitive emissions from other area sources. Two teams performed measurements using analytical instruments installed in two vehicles, to measure downwind concentrations of target (CH4) and tracer gases at distances of 1.2-3.5 km from the release locations. The controlled target gas release rates were either 5.3 or 10.9 kg CH4 h-1, and target and tracer gases were released at distances between 12 m and 140 m from each other. Five measurement campaigns were performed, where the plume was traversed between 2 and 31 times. The measured target gas emissions agreed well with the controlled releases, with rate differences no greater than 1.1 kg CH4 h-1 for Team A and 1.0 kg CH4 h-1 for Team B when quantifying a controlled release of 10.9 kg CH4 h-1. This corresponds to a maximum error of ±10%. A larger error of up to 18% was seen in the campaign with a lower target gas release rate (5.3 kg CH4 h-1). Using a cross plume integration method to calculate tracer gas to target gas ratios provided the most accurate results (lowest error), whereas larger errors (up to 49%) were observed when using other calculation methods. By establishment of an error budget and comparison with the measured error based on the release test, it could be concluded that following best practice when performing measurements, the overall error of a tracer gas dispersion measurement is very likely to be less than 20%.

Nitrogen mineralisation and greenhouse gas emission from the soil application of sludge from reed bed mineralisation systems.

A sludge treatment reed bed system (STRB) is a technology used for dewatering and stabilising sewage sludge via assisted biological mineralisation, which creates a sludge residue suitable for use as fertiliser on agricultural land. We evaluated the effect of sludge residue storage time (stabilisation time) for three STRBs on soil N mineralisation and CO2 and N2O emissions in soil. The experiment revealed that the N mineralisation rate and emissions of CO2 and N2O decreased as a function of treatment time in the STRBs. Mixed sludge residue (sludge residue subjected to different treatment times) for the three STRBs resulted in N mineralisation rates similar to the sludge residue subjected to a shorter treatment time but lower N2O emissions similar to the values of the older sludge residue. This finding reveals that combining fresh and more stabilised sludge residue ensures high N availability and reduces N2O emissions when applied to land.

Rapid biochemical methane potential prediction of urban organic waste with near-infrared reflectance spectroscopy.

The anaerobic digestibility of various biomass feedstocks in biogas plants is determined with biochemical methane potential (BMP) assays. However, experimental BMP analysis is time-consuming, costly and challenging to optimise stock management and feeding to achieve improved biogas production. The aim of the present study is to develop a fast and reliable model based on near-infrared reflectance spectroscopy (NIRS) for the BMP prediction of urban organic waste (UOW). The model comprised 87 UOW samples. Additionally, 88 plant biomass samples were included, to develop a combined model predicting BMP. The coefficient of determination (R2) and root mean square error in prediction (RMSEP) of the UOW model were 0.88 and 44 mL CH4/g VS, while the combined model was 0.89 and 50 mL CH4/g VS. Improved model performance was obtained for the two individual models compared to the combined version. The BMP prediction with NIRS was satisfactory and moderately successful.

Optimising the anaerobic co-digestion of urban organic waste using dynamic bioconversion mathematical modelling.

Mathematical anaerobic bioconversion models are often used as a convenient way to simulate the conversion of organic materials to biogas. The aim of the study was to apply a mathematical model for simulating the anaerobic co-digestion of various types of urban organic waste, in order to develop strategies for controlling and optimising the co-digestion process. The model parameters were maintained in the same way as the original dynamic bioconversion model, albeit with minor adjustments, to simulate the co-digestion of food and garden waste with mixed sludge from a wastewater treatment plant in a continuously stirred tank reactor. The model's outputs were validated with experimental results obtained in thermophilic conditions, with mixed sludge as a single substrate and urban organic waste as a co-substrate at hydraulic retention times of 30, 20, 15 and 10 days. The predicted performance parameter (methane productivity and yield) and operational parameter (concentration of ammonia and volatile fatty acid) values were reasonable and displayed good correlation and accuracy. The model was later applied to identify optimal scenarios for an urban organic waste co-digestion process. The simulation scenario analysis demonstrated that increasing the amount of mixed sludge in the co-substrate had a marginal effect on the reactor performance. In contrast, increasing the amount of food waste and garden waste resulted in improved performance.

Physico-chemical characterisation of material fractions in residual and source-segregated household waste in Denmark.

Physico-chemical waste composition data are paramount for the assessment and planning of waste management systems. However, the applicability of data is limited by the regional, temporal and technical scope of waste characterisation studies. As Danish and European legislation aims for higher recycling rates evaluation of source-segregation and recycling chains gain importance. This paper provides a consistent up-to-date dataset for 74 physico-chemical parameters in 49 material fractions from residual and 24 material fractions from source-segregated Danish household waste. Significant differences in the physico-chemical properties of residual and source-segregated waste fractions were found for many parameters related to organic matter, but also for elements of environmental concern. Considerable differences in potentially toxic metal concentrations between the individual recyclable fractions within one material type were observed. This indicates that careful planning and performance evaluation of recycling schemes are important to ensure a high quality of collected recyclables. Rare earth elements (REE) were quantified in all waste fractions analysed, with the highest concentrations of REE found in fractions with high content of mineral raw materials, soil materials and dust. The observed REE concentrations represent the background concentration level in non-hazardous waste materials that may serve as a reference point for future investigations related to hazardous waste management. The detailed dataset provided here can be used for assessments of waste management solutions in Denmark and for the evaluation of the quality of recyclable materials in waste.

Co-digestion of food and garden waste with mixed sludge from wastewater treatment in continuously stirred tank reactors.

Co-digestions of urban organic waste were conducted to investigate the effect of the mixing ratio between sludge, food waste, grass clippings and green waste at different hydraulic retention times (HRTs). Compared to the digestion of 100% sludge, the methane yield increased by 48% and 35%, when co-digesting sludge with food waste, grass clippings and garden waste with a corresponding %VS of 10:67.5:15.75:6.75 (R1) and 10:45:31.5:13.5 (R2), respectively. The methane yield remained constant at around 425 and 385 NmL CH4/g VS in R1 and R2, respectively, when the reactors were operated at HRTs of 15, 20 and 30 days. However, the methane yield dropped significantly to 356 (R1) and 315 (R2) NmL CH4/g VS when reducing the HRT to 10 days, indicating that the process was stressed. Since the methane production rate improved significantly with decreasing HRT, the trade-off between yield and productivity was obtained at 15 days HRT.

A comprehensive substance flow analysis of a municipal wastewater and sludge treatment plant.

The fate of total organic carbon, 32 elements (Al, Ag, As, Ba, Be, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, N, Na, Ni, P, Pb, S, Sb, Se, Sn, Sr, Ti, V, and Zn) and 4 groups of organic pollutants (linear alkylbenzene sulfonates, bis(2-ethylhexyl)phthalate, polychlorinated biphenyl and polycyclic aromatic hydrocarbons) in a conventional wastewater treatment plant were assessed. Mass balances showed reasonable closures for most of the elements. However, gaseous emissions were accompanied by large uncertainties and show the limitation of mass balance based substance flow analysis. Based on the assessment, it is evident that both inorganic and organic elements accumulated in the sewage sludge, with the exception of elements that are highly soluble or degradable by wastewater and sludge treatment processes. The majority of metals and metalloids were further accumulated in the incineration ash, while the organic pollutants were effectively destroyed by both biological and thermal processes. Side streams from the sludge treatment process (dewatering and incineration) back to the wastewater treatment represented less than 1% of the total volume entering the wastewater treatment processes, but represented significant substance flows. In contrast, the contribution by spent water from the flue gas treatment process was almost negligible. Screening of human and eco-toxicity by applying the consensus-based environmental impact assessment method USEtox addressing 15 inorganic constituents showed that removal of inorganic constituents by the wastewater treatment plant reduced the toxic impact potential by 87-92%.

Home composting as an alternative treatment option for organic household waste in Denmark: An environmental assessment using life cycle assessment-modelling.

An environmental assessment of the management of organic household waste (OHW) was performed from a life cycle perspective by means of the waste-life cycle assessment (LCA) model EASEWASTE. The focus was on home composting of OHW in Denmark and six different home composting units (with different input and different mixing frequencies) were modelled. In addition, incineration and landfilling was modelled as alternatives to home composting. The most important processes contributing to the environmental impact of home composting were identified as greenhouse gas (GHG) emissions (load) and the avoided emissions in relation to the substitution of fertiliser and peat when compost was used in hobby gardening (saving). The replacement of fertiliser and peat was also identified as one of the most sensible parameters, which could potentially have a significant environmental benefit. Many of the impact categories (especially human toxicity via water (HTw) and soil (HTs)) were affected by the heavy metal contents of the incoming OHW. The concentrations of heavy metals in the compost were below the threshold values for compost used on land and were thus not considered to constitute a problem. The GHG emissions were, on the other hand, dependent on the management of the composting units. The frequently mixed composting units had the highest GHG emissions. The environmental profiles of the home composting scenarios were in the order of -2 to 16 milli person equivalents (mPE) Mg(-1) wet waste (ww) for the non-toxic categories and -0.9 to 28mPEMg(-1) ww for the toxic categories. Home composting performed better than or as good as incineration and landfilling in several of the potential impact categories. One exception was the global warming (GW) category, in which incineration performed better due to the substitution of heat and electricity based on fossil fuels.