management system and the MARTES model [4] for the district
heating system including CHPs. In this studywaste streams suitable
for thermal and/or biological treatment (including sewage sludge
after wastewater treatment) are included whereas fractions for
material recycling are excluded.
ORWARE is a computer based tool for environmental and
economic systems analysis of waste management. It was first
developed for systems analysis of organic waste management,
hence the acronym ORWARE (OrganicWaste Research). The model
is designed for strategic long-term planning of recycling and waste
management and based upon static conditions and on linear
programming (LP). The ORWARE model has been developed since
the early 1990s in close cooperation between four different research
institutions in Sweden (Royal Institute of Technology, Swedish
Environmental Research Institute, Swedish Institute of Agricultural
and Environmental Engineering and Swedish University for Agricultural
Sciences). The waste management is followed from cradle
(waste sources) via collection and transport to treatment plants and
further to grave (utilisation of products from waste treatment).
Treatment facilities included are incineration with energy recovery,
composting, landfill, anaerobic digestion with biogas utilisation,
spreading of organic fertiliser on arable land, sewage treatment,
material recycling of plastic and paper packages, and some additional
technologies. The model delivers substance flows, distributed
to emissions to air and water, left in growing crops and in recycled
material. Energy flows such as energy use and recovered energy are
also provided. Single substances such as carbon dioxide or eutrophication
substances towater can be tracked, as well as the amount
of plant-available nutrients and emissions of different heavy metals.
Emissions are also characterised and weighted using Life Cycle
Impact Assessment. At the same time financial costs (investment
and operational costs) and environmental costs and revenues
including savings in the surrounding system can be calculated for
the whole management chain.
MARTES is a model for district heating systems with production
of heat, steam and electricity. The model simulates the use of
different plants to satisfy the demand for district heating during
a year. As a result the effects on costs and emissions are calculated,
based on the energy conversion in the district heating system. The
development of MARTES started on a mainframe computer at the
Department of Energy Conversion in 1983. It has been commercially
available on personal computer since 1990. Today it is the
most widely used tool for strategic planning of district heating
systems in Sweden, since it covers nearly 70% of the produced heat
[5]. The MARTES model captures operation of all facilities for
district heating generation, given an exogenously given total need
for heat. The heat demand is based on a load curve and described
with a detailed time slice division into day and night periods. The
model includes fuel and electricity prices and policy tools. The
simulated plants are modelled with efficiencies (with part load
performance for CHP plants), minimum load for operation, availability,
emissions of carbon dioxide, sulphur and nitrogen oxides.
Annual fixed costs for equipment purchase and installation as well
as variable and annual fixed costs for operation and maintenance
are also included in the model. The output from the model is heat
generation for all plants, power generation in CHPs, use of electricity
in heat pumps and electrical boilers, fuel consumption and
emissions to air.
As mentioned above the focus in the study has been the waste
treatment and district heating system in Gothenburg. However, to
generate a fully system analysis effects that occur in surrounding
systems also have to be considered, such as the transport sector
(biogas from waste substitutes petrol and diesel oil), the electricity
production system (electric power from waste incineration with
energy recovery replaces electricity generation from fossil fuels),
the agricultural sector (nutrients from anaerobic digestion of waste
and sludge are used instead of mineral fertiliser) etc. In this study;
two different types of scenarios that reflect the situation of year
2030 have been set up: local scenarios and external scenarios [6]. In
a local scenario we define the waste treatment processes that are
assumed to be in operation in Gothenburg’s waste treatment
system in year 2030 (e.g. waste incineration, anaerobic treatment).
Furthermore, an external scenario reflects the situation in the
surrounding systems (e.g. price of electricity, fuels and CO2-
allowances). The local scenarios thereby describe developments
that the actors in Gothenburg can influence, while the external
scenarios describe developments that the actors have to adapt to.
The main principles of the local scenarios that have been set up are
as follows:
- Business-as-usual: This local