Management of municipal solid waste is an efficient method to increase resource efficiency, as well as to replace fossil fuels with renewable energy sources due to that (1) waste to a large extent is renewable as it consists of food waste, paper, wood etc. and (2) when energy and materials are recovered from waste treatment, fossil fuels can be substituted. In this paper results from a comprehensive system study of future biological treatment of readily degradable waste in two Swedish regions are presented. Different collection and separation systems for food waste in households have been applied as well as technical improvements of the biogas process as to reduce environmental impact. The results show that central sorting of a mixed fraction into recyclables, combustibles, biowaste and inert is a competitive option compared to source separation. Use of pellets is beneficial compared to direct spreading as fertiliser. Fuel pellets seem to be the most favourable option, which to a large extent depends on the circumstances in the energy system. Separation and utilisation of nitrogen in the wet part of the digestion residue is made possible with a number of technologies which decreases environmental impact drastically, however to a substantial cost in some cases.

The number of horses in Sweden is increasing and according to estimated statistics from Swedish Board of Agriculture, there are an estimated amount of 360,000 horses in the country. These horses are found in different types of activities (agriculture, trail riding, trot and canter, etc.) and they generate large quantities of horse manure. Horse manure consists of feces, urine and bedding material which various bedding materials used to various amount. The management of horse manure causes environmental problems when emissions occur during decomposition of organic material, in addition to nutrients not being recycled. The interest for horse manure be subject to anaerobic digestion and thereby produce biogas has increased with the increased interest in biogas as a renewable fuel.

This study has aimed to highlight the environmental impact of different ways to treat horse manure from a system perspective. Special attention has been focused on the involve­ment of different types of litter/bedding material and how it affects the effective­ness of various treatment processes. The treatment methods investigated are

1. Unmanged composting
2. Managed Composting
3. Large-scale incineration in a waste fired CHP plant
4. Drying and small-scale combustion
5. Solid state anaerobic digestion
6. Liquid state anaerobic digestion with and without thermal pre-treatment

Following significant data uncertainty in the survey, the results are only indicative, but they still point to large-scale incineration as an environmentally sound method. An excep­tion is the contribution to climate impact where digestion in different forms are preferred. Based on the study of various bedding materials, paper pellet appear as an interesting alternative to move forward with.

The overall conclusion is that more research is needed to ensure the quality of future surveys, thus an overall research effort from horse management to waste management.

Horse manure consists of feces, urine, and varying amounts of various bedding materials. The management of horse manure causes environmental problems when emissions occur during the decomposition of organic material, in addition to nutrients not being recycled. The interest in horse manure undergoing anaerobic digestion and thereby producing biogas has increased with an increasing interest in biogas as a renewable fuel. This study aims to highlight the environmental impact of different treatment options for horse manure from a system perspective. The treatment methods investigated are: (1) unmanaged composting; (2) managed composting; (3) large-scale incineration in a waste-fired combined heat and power (CHP) plant; (4) drying and small-scale combustion; and (5) liquid anaerobic digestion with thermal pre-treatment. Following significant data uncertainty in the survey, the results are only indicative. No clear conclusions can be drawn regarding any preference in treatment methods, with the exception of their climate impact, for which anaerobic digestion is preferred. The overall conclusion is that more research is needed to ensure the quality of future surveys, thus an overall research effort from horse management to waste management.

In horse keeping horse manure is produced, which can be utilized as a fertilizer or considered a waste. Horse manure constitutes a resource in terms of both plant nutrients and energy. In addition energy policies and objectives aim at replacing fossil fuels with renewable energy sources. The interest to improve resource recovery of horse manure increases due various incentives for renewable vehicle fuels, legal requirements on management of manure, and environmental impact from current horse manure management.

This thesis aims at describing horse manure management in a life cycle perspective. This is made by (1) identifying factors in horse keeping affect­ing the possibility to use horse manure as a biogas feedstock and to recycle plant nutrients, (2) analysing factors in anaerobic digestion with influence on methane potential and biofertilizer nutrient content and (3) comparing the environmental impact from different horse manure treatment methods. Literature reviews, systematic combining, and simulations have been used as research methods.

The results show that horse keeping activities such as feeding, indoor keeping, outdoor keeping and manure storage affect the amount and charac­teristics of horse manure and thereby also the possibilities for anaerobic digestion horse manure. Transport affects the collected amount and spread­ing affects loss of nutrients and nutrient recycling. Simulation results in­dicate the highest methane yield and energy balance from paper bedding, while straw and peat gave a higher nutrient content of the biofertilizer. The highest methane yield was achieved with a low rate of bedding, which in the cases of woodchips and paper is also preferable for plant nutrient recycling. Still, results indicate the best energy balance from anaerobic digestion with a high ratio of bedding. The environmental impact assessment indicates a reduction in global warming potential for anaerobic digestion compared to incineration or composting.

The number of horses in society is increasing and today, according to Swedish Board of Agriculture, there are approximately 360,000 horses in Sweden, where three-quarters are found in urban or near-urban environments. All these horses will, according to calcula­tions, give rise to a total amount of manure of up to 1.4 million tons per year. If this manure is digested efficiently, this corresponds to an annual biogas production of 641 GWh, which is almost half of all biogas produced in Sweden in 2010. Although there are some practical limitations on how much of the potential that can be exploited, there is nevertheless a significant potential for increased use of renewable energy. By collecting manure and digesting it, three environmental benefits can be achieved:

1. Emissions from conventional management where the manure is piled and stored, or spontaneously composted, are avoided
2. Anaerobic digestion of manure produces biogas that can be used to generate elec­tricity and heat and, after upgrading (purification and pressure increase), as vehicle fuel; thereby fossil fuel emissions are reduced
3. The resulting digestate can be used in agriculture, thereby replacing chemical ferti­lizer which provides additional environmental benefits

Despite all these possibilities there are some obstacles and gaps in knowledge. This report is a systematic review of the state of knowledge about horse manure management, pre­treatment methods, digestion methods of horse manure, as well as aspects of the prolifer­ation of bio-fertilizer from horse manure. This part is mainly qualitative descriptions while subsequent reports present indicative calculations of the environmental benefits of different ways to design the management.

The conclusions are that there are many factors that point to extract energy from horse manure, e.g. there are significant amounts of manure relatively close to urban areas, the straw bedding materials provide a supplement in biogas production, there is plenty of land for spreading digestate, and an improved horse manure management is also a good water protection measure. Drawbacks are that the digestion of horse manure is relatively untested and it is difficult to assess how increased waste management costs affect the horse industry. Another conclusion is the general lack of knowledge of horse manure from an environmental perspective at a level required for reliable environmental assess­ments. Nevertheless we hope to be able to propose system solutions which to a greater extent than previously should prove to work technically and be economically feasible. If these systems are translated into practical reality, environmental gains can be made through reduced environmental impact, reduced eutrophication, increased biodiversity and reduced use of finite resources.

A transition to renewable energy sources and a circular economy has increased interest in renewable resources not usually considered as energy sources or plant nutrient resources. Horse manure exemplifies this, as it is sometimes recycled but not often used for energy purposes. The purpose of this study was to explore horse manure management in a Swedish municipality and prospects for energy recovery. The case study includes a survey of horse manure practices, environmental assessment of horse manure treatment in a biogas plant, including associated transport, compared to on-site unmanaged composting, and finally a simplified economic analysis. It was found that horse manure management was characterized by indoor collection of manure most of the year and storage on concrete slabs or in containers, followed by direct application on arable land. Softwood was predominantly used as bedding, and bedding accounted for a relatively small proportion (13%) of the total mix. Anaerobic digestion was indicated to reduce potential environmental impact in comparison to unmanaged composting, mainly due to biogas substituting use of fossil fuels. The relative environmental impact from transport of manure from horse facilities to anaerobic digestion plant was small. Results also indicate a relatively high cost for horse keepers to change from composting on site to anaerobic digestion in a centralized plant.

Management of horse manure is seldom subject to energy recovery. In the current project solutions for energy recovery of horse manure, with a focus on biogas production as the process not only recovers energy but also closes nutrient cycles, are identified and asses­sed from an environmental point of view. The number of horses in society is increasing. Today, according to Statistics Sweden, there are more than 360,000 horses in Sweden, of which three-quarters are situated in urban or near-urban environments. With a dry matter content of 40 %, this equates to a quantity of 1,360 tonnes of horse manure per annum and corresponds to an annual biogas production of 641 GWh, which corresponds to almost 40 % of all biogas produced in Sweden in 2013. Although there are some practical limitations on how much of that potential can be exploited, this is still a significant potential for increased use of renewable energy. Collecting manure and anaerobically digesting it achieves three environmental benefits:

1. Emissions from conventional management, where the manure is piled and stored, or spontaneously composted or decomposed, are avoided.
2. Anaerobic digestion of manure produces biogas that can be utilised to generate electricity and/or heat or, after upgrading (purification and pressure increase), as vehicle fuel; thereby emissions from fossil fuels are reduced.
3. Following the process, the resulting digestate can be used in agriculture, thereby re­placing chemical fertiliser and providing additional environmental benefits.

The aim of this project is to find a greater breadth of system solutions than previously, solutions that are proven to function technically and be economically feasible. If these systems are translated into practical reality, environmental gains are made, for example, through reduced environmental impact such as reduced eutrophication and reduced use of finite resources.

This report documents a data inventory made for the life-cycle assessment (LCA) of horse manure management systems in the Gävleborg region, Sweden. The overall result is that data are scarce for all parts of the system, from feedstock characteristics to waste treatment methods as well as utilisation of biofertiliser. There are few plants for solid state anaerobic digestion, at least using horse manure as substrate, and little is known about emissions from current manure practise. Moreover, as the number and location of horses are hard to estimate, the forthcoming systems analysis has to be made for a hypo­thetical amount of horse manure and emissions etc. have to be expressed per ton VS. Given these uncertainties the systems analysis will just give indicative results.

The aim of this work was to study the dilute acid pretreatment of rice straw (RS) and fermentable sugar recovery at high solid loadings at pilot scale. A series of pretreatment experiments were performed on RS resulting in >25 wt% solids followed by enzymatic hydrolysis without solid-liquid separation at 20 and 25 wt% using 10 FPU/g of the pretreated residue. The overall sugar recovery including the sugars released in pretreatment and enzymatic hydrolysis was calculated along with a mass balance. Accordingly, the optimized conditions, i.e. 0.35 wt% acid, 162 °C and 10 min were identified. The final glucose and xylose concentrations obtained were 83.3 and 31.9 g/L respectively resulting in total concentration of 115.2 g/L, with a potential to produce >50 g/L of ethanol. This is the first report on pilot scale study on acid pretreatment of RS in a screw feeder horizontal reactor followed by enzymatic hydrolysis at high solid loadings.

The emissions of greenhouse gases need to decrease rapidly over the coming decades. Sweden has set the target to achieve net zero emissions by 2045. The industrial sector plays a crucial role in that conversion by reducing its energy needs and to convert from fossil fuels to renewables.

This conversion will require a more robust and reliable energy system were todays centralized system has been supplemented by small decentralized production facilities. To produce heat and power closer to the consumers means less transmission losses. Small scale combined heat and power (CHP) production based on biofuels or excess heat could be a solution to reduce greenhouse gas emissions.

The purpose of this paper is to evaluate the possibility for a mid-size Swedish industrial company to produce its own base load of heat and power with a conventional Rankine cycle. Also to evaluate the production costs depending on the size of the plant.

The work has consisted of data collection from different manufacturers of steam turbines and steam boilers, a calculation model has been made in Excel to compare different plant sizes and in different operating scenarios. Economical evaluations has been made with the Pay-off method and the net present value method (NPV).

The result shows that production costs for facilities with steam turbines in the size range of 10 – 100 kWel is well below the price of bought electricity and district heating. The economical evaluation generally shows on short pay-off times and positive NPV.

A comparison of the CHP plants shows that the electric efficiency is low and the total efficiency sometimes can be lower than for the existing heat supplier of the company. This means that a switch to local CHP will have a negative impact from a system perspective, because of the increased use of primary energy resources.

There is many parameters that affects the performance of a CHP plant but the most crucial is the operation time. To have a continuous operation over a major part of the year has a great impact on the economic performance. The low electric efficiency means that the major part of the savings gets on the heat production. This means that the CHP plant should be dimensioned to replace primarily the heat requirement.

Most developing countries of the world still uses biomass for domestic energy, this is mostly used in the rural areas and using our case study which is Nigeria and China. We have been able to establish the potential of biomass production energy use by looking at calorific values of some biomass such As-harvested wood, Dry wood, Straw Miscanthus Coal  which was discussed on the introduction part of this thesis.

Cotton stalk is a holocellulose rich, inexpensive agricultural residue available in surplus without any competitive uses neither as food nor as animal fodder. These aspectshold high potential for cotton stalk as a biomass to be suitable for ethanol production. Dilute acid pretreatment conditions on bench scale have been optimized for cotton stalk by Response Surface Methodology (RSM) using Central Composite Design (CCD). Effect of four pretreatment process variables viz. temperature, acid concentration, time of reaction and stirring speed has been optimized for maximum enzymatic sugar release during the subsequent enzymatic saccharification. Under the optimized pretreatment conditions, i.e., temperature: 157. °C, acid concentration: 1.07% (w/w),and time: 20 min, enzymatic sugar releasewas found to be 684 mg/g of dry pretreated biomass. A correlation of hemicellulose removal and inhibitor formation with combined severity factor (CSF) was drawn. Mass balance carried out for the pretreatment step under optimized conditions resulted in 68.35 and 8.31% of xylose and glucose saccharificationyieldsrespectively. Subsequent enzymatic saccharification yieldsofglucose and xylose were 93.56 and 19.93% respectively. The overall saccharification yield integrating pretreatment and enzymatic hydrolysis of cotton stalk was 91.06%. Physicochemical characterization of native and pretreated biomass was carried out by compositional analysis, FT-IR and XRD revealing significant changes in biomassproperties responsible for improved saccharification efficiency.

The environmental sustainability of cellulosic ethanol production from rice straw in India is conducted using life cycle assessment (LCA). Greenhouse gas (GHG) emissions, net energy ratio (NER) and net energy balance (NEB) are studied for ethanol production system using two diverse pretreatment technologies, i.e. dilute acid (DA) and steam explosion (SE) followed by separate hydrolysis and fermentation. 1 ton of rice straw is the reference flow of study and 1 MJ transportation fuel is the functional unit while comparing the results with gasoline. The inventory data is collected based on several experiments conducted at our pilot plant and is a novel contribution to country specific LCA. Using DA and SE, the ethanol yields from the processing of 1 ton straw are 239 and 253 L and life cycle GHG emissions are 292 and 288 kg CO₂ eq./ton straw respectively. The results indicated that production of enzyme used in hydrolysis is the major contributor to GHG emissions in both DA (54%) and SE (57%) methods of ethanol production. The net energy input during the life cycle of ethanol is 1736 and 1377 MJ/ton straw in DA and SE respectively. The major GHG emissions and energy benefits are obtained using lignin produced in the plant to generate electricity resulting in displacement of the coal based electricity. With a higher xylose recovery in the SE, it gives larger amount of ethanol and also generates more surplus electricity. Enzyme production and its use are identified as GHG emission and energy consumption hotspot in the ethanol production process. While comparing the results with gasoline, DA and SE resulted in a reduction of 77 and 89% GHG emissions and NER of 2.3 and 2.7 respectively. The E5 blending would reduce GHG emissions by 4.3% (DA) and 4.8% (SE) whereas; E20 blend would lead to a reduction of 17.4% (DA) and 18.8% (SE) respectively. Sensitivity analysis indicates that with every 12.5% increase in the price of rice straw from the base case, there is a 2.3% increase in GHG emissions and vice versa. 1 FPU/g WIS increase during hydrolysis gives 2.9% increase in ethanol production, but at the same time there is an increase of 5% emissions from enzyme production. The results of the study conclude that cellulosic ethanol production technology in India is sustainable from GHG reduction and energy efficiency perspective.

Dilute acid (DA) pretreatment results in the formation of inhibitory compounds and pseudo-lignin along with the burden of unnecessary materials like ash, extractive, lignin or their condensed products that reduces the conversion efficiency of cellulose to monomeric sugar. Indian Oil Corporation Limited (IOCL) has developed a modified pretreatment (MP) in order to reduce the enzyme dosage during ethanol production. This method uses extraction of biomass in water and varying alkali concentration of 0.2, 0.4 and 0.5%, prior to pretreatment as a strategy to reduce the enzyme dosage and improve the ethanol yield. The environmental and economic impact of these MP scenarios in comparison with conventional pretreatment (CP) is studied. The ethanol production increases from 218 to 267 L using MP. The introduction of extraction step prior to DA pretreatment fulfills the objective of reducing enzyme dosage by 23–39%. However, overall life cycle assessment (LCA) results revealed that performance of MP2, MP3 and MP4 is on a negative side in all the environmental impact categories as compared to CP due to the use of alkali, where a huge amount of emissions are released during the production stage. Overall, MP1 using water as a media for extraction is the most environmentally suitable pretreatment process for ethanol production. Life cycle costing (LCC) results showed that cost of 1 L ethanol production could be lowered down from 0.87 to 0.70 United States Dollar (USD) using MP1 scenario. From an environment and economic perspective, it is recommended to use only water as an extraction media for biomass, as this can reduce the enzyme dosage, emissions and cost.