e19cb7de-7733-4e86-a194-4d7009328575Enclosed composting (incl. compost application and crediting)enclosed composting plant, without collection and transport of waste but including the production of good quality compost and the utilisation of compostat plantnoneEnd-of-life treatmentLandfillingThe modelled enclosed composting plant is defined based on the treatment of average biodegradable waste consisting of biodegradable garden and park waste, food and kitchen waste (It does not include forestry or agricultural residues, manure, sewage sludge, or other biodegradable waste such as natural textiles, paper or processed wood).
The used model and the used settings allows to attribute the environmental burden (emissions and also resource consumption of auxiliaries and energy) as well as the credits for compost utilisation according to a specific input composition (defined via dry matter, C:N ratio and material composition). Default values for the average biodegradable waste are used in the specific model.
Therefore the LCI data is valid for the enclosed composting of average biodegradable waste The following technology description explains the settings and technology of the average enclosed composting plant used to generate the LCI data set. The data set covers all relevant process steps for the composting and corresponding processes, such as pre-treatment, post-treatment, sieving, compost utilisation and crediting of substituted Humus (it is assumed that the application of compost is done to sustain the C and N reservoir of the soil) as well as NPK fertilisers. The inventory is mainly based on extended literature data as well as laboratory analysis andreal plant data. The system is partly terminated (open inputs electricity, fuel).0The data set represents the treatment of biodegradable waste in enclosed composting plants. The assumptions concerning waste composition or rotting process are based on Central European conditions. Data are valid at least for Germany, Austria and SwitzerlandThe data set represents theenclosed composting of an average mixture of biodegradable waste consisting of biodegradable garden and park waste as well as food and kitchen waste with a content of 35 % Dry matter and a C:N ratio of 26.8. The composition of the biowaste was defined based on literature.
Enclosed composting systems partly or fully take place in closed halls or so called composting boxes or rotting tunnels. The advantage of closed systems is that exhaust air can be collected and cleaned. Those systems are especially used for the composting of sewage sludge or fermentation residues, to reduce the emission of ammonia (odour nuisance) but are also common for biowaste. Enclosed composting uses the same process of aerobic decomposition of organic matter by bacteria and other microorganisms as does open composting and is also referred to as 'In-Vessel Composting'.
It is assumed that up to 20% of Methane-Emissions are degraded by biofilters. The most positive effect can be seen by the reduction of ammonia (90%-100%). This can also be applied by the use of acid scrubbers. Mean technology was assumed for air purification.
Environmental impacts for waste collection and transport of the waste are not included in the data set.
The process starts with the pre-treatment a process step used for the adjustment and optimization of the input substrate (=rotting feedstock) before the rotting process. It can be described as a mixing process of available input materials (e.g. green waste, garden waste, structure materials, sieving rest, water,…).
For the composting model the process of pre-treatment determines purpose of the entire model which can also be seen as the functional unit: Composting of x kg biowaste. Basic input flow is biowaste from Austria.
IMPORTANT for the application of this process routines is to control the process relevant parameters for the rotting process which are:
• C/N ratio = should be between 20 and 40
• DM_in_ro = should be between 25 and 50 percent
Rotting is the core process of the composting model. The rotting process is an aerobic biological degradation and alteration process influencing nearly solely the organic compounds of the rotting feedstock.
Inputs for the rotting process is rotting feedstock from pre-treatment as well as energy and fuels: Electricity and fuel (for wheel loader) is needed through the entire composing process (pre-treatment, rotting and post-treatment). Default values for power and diesel consumption are literature
The used degradation rate in the compost modell is 60 % for carbon and 50% for nitrogen. Leachate is collected and used for irrigation of windrow piles. Screenings are used again as bulking material.
Emissions from the composting process are based on Literature.
The following emissions factors are applied: CH4: 710 g/ t waste input; N2O 68 g/t waste input, NH3 63 g/waste input and NMVOC 60 g/t waste input. Specific emission factors were defined based on C and N degradation rate.
Emissions containing these substances have been allocated to the specific waste input. This is done by calculation factors. These factors determine e.g. how much of C is emitted as CH4.
N emissions not emitted as N2O or NH3 are assumed to be N2 emissions with no further environmental relevance. Therewith N2 emissions are neglected. Calculation factors have been applied for: CH4, NMVOC, NH3, N2O. These factors include the information from different composting technologies
Post-treatment is necessary to enable defined compost quality. It can be described as a sieving process.
Output fractions are compost, sieving rest and impurities (not applied for this process). Mass substances are divided between compost and sieving rest.
Compost utilization means the application of compost on agricultural land. By using compost as fertilizer and soil conditioner an additional biological degradation process was taken into account. According to literature no Methane is emitted. This means that the entire mass of C in compost which is not fixed as Humus-C is emitted as CO2. The content of Humus-C is 58%. CO2 emissions are calculated automatically.
The emissions based on the remaining nitrogen content follow Knappe et al. (2012) with 1% N2O-N, 1% NO-N, 8% N2-N and 1 % NH3-N. Problematic compost elements e.g. heavy metals, are also emitted by compost utilization on agricultural land. Generally all heavy metals entering the composting process can be found in the compost product and therewith emitted to soil.
Crediting valuable properties of compost is quiet complicated as it has different influences on agricultural land or soil depending of its type of application or the type of soil. For the BOKU composting model a simplified approach was applied using the basic methodology of Knappe et al. (2012). In this conservative approach it is assumed that the entire amount of compost is used on agricultural land for Humus-reproduction. This means that the application of compost is done to sustain the C and N reservoir of the soil. Humus-reproduction is modelled by the estimation of equivalent processes which are 50% cultivation of intertillage and 50% usage of straw. This means that for agricultural use of soil without compost utilization intertillage has to be done to sustain Humus-C in soil. Usage of straw means that if compost is used straw can be used for other purposes - in this case litter for horse stables. Therefore the production of wooden horse bedding is avoided.
Additionally the credits for substituted NPK fertilizers are calculated based on the compost specifications
As NH3 emission from compost utilization are taken into account, NH3 emission from N fertilizer also have to be allocated as avoided emissions. For this model it is assumed that 10% of the substituted N fertilizer would be emitted as NH3.Truck, Euro 4, 20 - 26t gross weight / 17.3t payload capacityElectricity grid mixDiesel mix at refineryWood (natural) in waste incineration plantProcess steam from hard coal 95%Ammonia liquid (NH3) with CO2 recovery, by-product carbon dioxide (economic allocation)Potassium chloride (KCl/MOP, 60% K2O)Standard end-of-life treatment service for specific waste via composting.flow chart enclosed composting agg level 3.jpgThe model is built for the described technology and verified with measured data from several Austrian composting plants and further literature data.
The C:N ratio of the input as well as the dry matter is calculated based on the specification of the input. The material flow in the plant is calculated using individual transfer coefficients for every element and stage of the plant.
For the input specification in the model the following elements and compounds are addressed: Al, As, C (fossil, biogenic, inorganic), Ca, Cl, Cd, Cr, Cu, Fe, H, H2O, Hg, K, Mg, Mn, Mo, N, Ni, O, Pb, S, Si, Sn, V, Zn.
The modeled emissions to air during rotting and compost utilisation are: NH3, CO2, CH4, N2O, NMVOC Al, As, (fossil, biogenic, inorganic), Cl, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, NO, Ni, O, Pb, S, Si, Sn, V, Zn. In addition sieving rest and impurities are modelled. The transfer of the elements and substances into the different mediums is done with transfer coefficients based on real plant data, literature and experts. Some of the elements respectively tracked substances leaving the system are input dependent. That means there is a stoichiometrical correlation between input and output. For other input the relations are depending on the used technology. The output of these substances are a function of the used technology and therefore independent of the specific input. Input dependent parameters are for example the input of C or N and metals and the emissions caused by these elements. The amount of sieving rest is also input dependent.LCI resultAttributionalnoneAllocation - net calorific valueAllocation - massDirect land use change: GHG emissions from direct LUC allocated to good/service for 20 years after the LUC occurs.
Carbon storage and delayed emissions: credits associated with temporary (carbon) storage or delayed emissions are not considered in the calculation of the Global Warming Potential impacts for the default impact categories.
Emissions off-setting: not included
Fossil and biogenic carbon emissions and removals: removals and emissions are modelled as follows: All GHG emissions from fossil fuels (including peat and limestone) are modelled consistently with the ILCD list of elementary flows. In the case that the emissions refer to the molecules CO2 and CH4, they are modelled as ‘carbon dioxide (fossil)’ and ‘methane (fossil)’. Biogenic uptake and emissions are modelled separately. For land use change, all carbon emissions and uptakes are inventoried separately for each of the elementary flows. Soil carbon accumulation (uptake) via improved agricultural management is excluded from the model.noneGaBi Modelling Principles 2007All elements available in the model as input parameters are specified for the biowaste and therefore included. Coverage of at least 95% of mass and energy of the input and output flows, and 98% of their environmental relevance (according to expert judgment)noneThe transfer coefficients for the elements (used to allocate the different elements and substances to the different mediums air, compost, soil) of the composting plant are determined based on real plant data and a comprehensive literature research. LCI modeling is fully consistent.nonenonenoneBoldrin A., Andersen J.K., Moller J., Chistensen T.H., Favoino E. (2009)Boldrin A., Neidel T.L., Damgaard A., Bhander G.S., Møller J., Christensen T.H. (2011)Knappe F., Vogt R., Lazar S., Höke S. (2012)Amlinger F., Peyr S., Cuhls C. (2008)Hanc A., Novak P., Dvorak M., Habart J., Svehla P. (2011)Ortner M., Müller W., Bockreis A. (2013)NeuCuhls C., Mähl B., Berkau S., Clemens J. (2008)Kresse, A., BÜSCHER, W. (2008)Trimborn M., Wulf S. (2006)95.0noneThe data set represents an end of-life inventory for the enclosed composting of a specific mixture of biodegradable wastes (food waste kitchen, garden waste..) in an average composting plant with average exhaust air purification. The data set includes the emissions and resource consumption for the composting process. All credits for compost utilisation are included. Necessary electricity are unconnected (partly terminated). It should be considered that this data set is an approximation to reality. The used model of an average enclosed composting plant and the average composition of biowaste do not exist in reality and efficiencies, emission values, transfer coefficients and elementary composition will differ if a specific plant is used. This data set can be used for the composting of the mentioned and specified waste in the specified region.All relevant flows quantifiedBOKU2020-01-01T00:00:00.000ILCD format 1.1BOKU2020-01-01T00:00:00.00000.00.001Data set finalised; entirely publishedBOKUtrueOtherGaBi (source code, database including extension modules and single data sets, documentation) remains property of thinkstep AG. thinkstep AG delivers GaBi licenses comprising data storage medium and manual as ordered by the customer. The license guarantees the right of use for one installation of GaBi. Further installations using the same license are not permitted. Additional licenses are only valid if the licensee holds at least one main license. Licenses are not transferable and must only be used within the licensee's organisation. Data sets may be copied for internal use. The number of copies is restricted to the number of licenses of the software system GaBi the licensee owns. The right of use is exclusively valid for the licensee. All rights reserved.BiowasteInput1000.01000.00Mixed primary / secondaryEstimatedvaluable