• Energy Research

Abstract Energy decisions play an essential role in reducing greenhouse gas (GHG) emissions in the transportation sector. Biogas is a renewable energy source and can be used as an energy source for gas-operated cars or for electric cars. This paper compares different ways to use biogas, which is produced on a medium scale anaerobic digestion plants, as an energy source for transportation. The research is conducted from an economic and environmental point of view, and the option to deliver upgraded biogas via a natural gas grid is taken into account. Different processes for the use of biogas for transportation purposes are compared using life cycle assessment (LCA) methods in the Finnish operational environment. It seems that the most economical way is to use biogas in gas-operated cars due to the high price of methane for vehicle fuel use. A new feed-in tariff for electricity produced with biogas will, however, have highly positive economic effects on electricity production from biogas. From the environmental point of view, the highest CO2 reductions are gained when biogas is used in gas-operated cars or in CHP plants for power and heat production. During the transition stage, it might be reasonable to use biogas in gas-operated cars and most importantly in heavy vehicles to reduce GHG and local pollutants rapidly. If biogas production is located near a natural gas grid, the biogas can be delivered effectively via the natural gas grid. The use of biogas in gas-operated cars is an effective way to reduce carbon dioxide significantly in the transportation sector.

For the estimation of greenhouse gas emissions from waste incineration it is essential to know the share of the renewable energy content of the combusted waste. The composition and heating value information is generally available, but the renewable energy share or heating values of different fractions of waste have rarely been determined. In this study, data from Finnish studies concerning the composition and energy content of mixed MSW were collected, new experimental data on the compositions, heating values and renewable share of energy were presented and the results were compared to the estimations concluded from earlier international studies. In the town of Lappeenranta in south-eastern Finland, the share of renewable energy ranged between 25% and 34% in the energy content tests implemented for two sample trucks. The heating values of the waste and fractions of plastic waste were high in the samples compared to the earlier studies in Finland. These high values were caused by good source separation and led to a low share of renewable energy content in the waste. The results showed that in mixed municipal solid waste the renewable share of the energy content can be significantly lower than the general assumptions (50-60%) when the source separation of organic waste, paper and cardboard is carried out successfully. The number of samples was however small for making extensive conclusions on the results concerning the heating values and renewable share of energy and additional research is needed for this purpose.

Municipal solid waste (MSW) management is becoming increasingly popular around the world as a means of accommodating the increasing amounts of waste that the growing global population generates. China currently produces more MSW than any other country. As such, this area of the world is facing challenges on an unprecedented scale. MSW management in China is highly dependent on landfilling, and the development of sanitary landfills is currently a top priority for the Chinese government. Hangzhou is one of the most developed cities in China. In fact, in 2013, the amount of incinerated MSW in Hangzhou represented 56% of total MSW. MSW incineration is primarily performed via a process of co-incineration with coal because MSW has a low heating value. This paper employs a environmental impact assessment by LCA program to determine whether refuse-derived fuel (RDF) production and incineration can have a more positive impact on the environment than the co-incineration of MSW with coal in Hangzhou, China. According to the results, RDF production and incineration could improve Hangzhou’s MSW management global warming potential from -33% to 0%, the acidification potential from -90% to 34%, and the eutrophication potential from -1 200% to 350% in comparison to the co-incineration of MSW with coal. The treatment of organic reject material from RDF production has a significant effect on the results; as such, it should be utilized in energy production rather than landfilled.

The SISMan (Simple Integrated System Management) decision-aid model is introduced in this paper. The SISMan model is used in a demonstration of evaluating the viability of adding an Energy-from-Waste (EfW) plant to an existing municipal energy supply system. The integrated system utilizes co-generation in heat and electricity production. The evaluation is carried out by calculating the energy and money flows for the integrated system and comparing the results to the original system values. No "competing technologies" to the EfW alternative are presented; the evaluation is carried out simply by comparing the original ("existing") system flows to the integrated system flows. The results show that in certain conditions it is feasible to integrate an EfW plant with the existing municipal energy supply system in Finland. However, the conditions for a viable integration may not be so easy to fulfill.

Abstract Forest biomass is used in many countries as an abundant and easily accessible source of renewable energy. While forest biomass has certain advantages in terms of carbon sink capability, it cannot be considered an emission-free energy source, and the environmental differences among various forest biomass sources have been unclear. This study uses life cycle assessment for two purposes. The first is to quantify the environmental impacts of the energy production of a small-scale, combined heat and power production plant utilizing different forest biomasses. The second aim is to estimate the change in environmental impacts on district heat production from natural gas when partially replacing it by heat from the combined heat and power plant. The environmental impacts include global warming potential, acidification potential, and eutrophication potential. The calculated environmental impacts of utilizing different forest biofuels in the CHP plant in relation to produced energy are 2.2–5.1 gCO2,eq./MJenergy excluding biogenic carbon emission, 59–66 gCO2,eq./MJenergy with biogenic carbon emission, and 133–175 mgSO2,eq./MJenergy and 18–22 mgPO34-,eq./MJenergy with pellets, showing the highest values. The results indicate that by using forest biomass instead of natural gas in energy production, the global climate impacts are reduced when biogenic carbon is excluded, while the local effects are higher (acidification potential and eutrophication potential). Including biogenic carbon reduces the calculated climate benefit since the total emissions end up being 4–7% over those of natural gas use. The potential benefits need to be weighed against the possible drawbacks.

This study systematically assessed and compared four ash recycling possibilities, namely forest fertilization, landfill construction, road construction, and road stabilization through the use of cost-benefit analysis and life cycle assessment methods. The results indicated that forest fertilization with ash was the most economically attractive method with a 60% increase in the net present value compared to ash landfilling, while reducing the environmental impact by 0.3%. On the contrary, road construction with ash resulted in a 13% reduction in the environmental impact and an increase in net present value of 25%. Landfill construction with ash was overall the least attractive proposition.

Based on mass and energy balance calculations, this work investigates the possibility of recovering heat and nutrients (nitrogen and phosphorus) from municipal sewage sludge using pyrolysis or combustion in combination with a gas scrubbing technology. Considering a wastewater treatment plant (WWTP) with 65,000 t/a of mechanically dewatered digestate (29% total solids), 550 t/a nitrogen and 500 t/a phosphorus were recovered from the 4900 t/a total nitrogen and 600 t/a total phosphorus that entered the WWTP. Overall, 3600 t/a (73%) of total nitrogen was lost to the air (as N2) and clean water, while 90 t/a (15%) of total phosphorus was lost to clean water released by the WWTP. Both in combustion and in pyrolysis, the nitrogen (3%) released within thermal drying fumes was recovered through condensate stripping and subsequent gas scrubbing, and together with the recovery of nitrogen from WWTP reject water, a total of 3500 t/a of ammonium sulfate fertilizer can be produced. Furthermore, 120 GWh/a of district heat and 9700 t/a of ash with 500 t/a phosphorus were obtained in the combustion scenario and 12,000 t/a of biochar with 500 t/a phosphorus was obtained in the pyrolysis scenario. The addition of a stripper and a scrubber for nitrogen recovery increases the total electricity consumption in both scenarios. According to an approximate cost estimation, combustion and pyrolysis require annual investment costs of 2–4 M EUR/a and 2–3 M EUR/a, respectively, while 3–5 M EUR/a and 3–3.5 M EUR/a will be generated as revenues from the products.

Pallets are the tiny cogs in the machine that drive transportation in the global economy. The profusion of pallets in today’s supply chain warrants the investigation and discussion of their respective environmental impacts. This paper reviews the life cycle assessment studies analyzing the environmental impacts of pallets with the intent of providing insights into the methodological choices made, as well as compiling the inventory data from the studies reviewed. The study is a meta-analysis of eleven scientific articles, two conference articles, two peer-reviewed reports, and one thesis. The review was implemented to identify the key methodological choices made in those studies, such as their goals, functional units, system boundaries, inventory data, life cycle impact assessment (LCIA) procedures, and results. The 16 studies reviewed cumulatively analyzed 43 pallets. Mostly pooled (n = 22/43), block-type (n = 13/43), and wooden (n = 32/43) pallets with dimensions of 1219 mm × 1016 mm or 48 in. × 40 in. (n = 15/43) were studied. Most of the studies represented pallet markets in the United States (n = 9/16). Load-based (e.g., 1000 kg of products delivered), trip-based (e.g., 1000 trips), and pallet-based (e.g., one pallet) functional units were declared. A trip-based functional unit seems the most appropriate for accounting of the function of the pallets, as its purpose is to carry goods and facilitate the transportation of cargo. A significant amount of primary inventory data on the production and repair of wooden and plastic pallets are available, yet there are significant variations in the data. Data on pallets made of wood–polymer composites was largely missing.