Ilze Dzene

Waste-to-biomethane Concept Application: A Case Study of Valmiera City in Latvia

Abstract The current needs of sustainable urban development are rising. As the transport sector expands, emissions continue to rise. Due to their negative impact on human health and the environment, air quality requirements are becoming more and more stringent. At the same time, the amount of waste is increasing. Europe Union policies attempt to relieve the pressure that these two stressors place on urban systems as they themselves expand. Today different solutions are available to decrease greenhouse gas emissions, increase air quality and improve waste management systems. Among them, waste-to-biomethane for use in urban systems deserves more attention. The paper focuses on application of the concept of waste-to-biomethane and the case study of Valmiera is evaluated. The results show that the application of the waste-to-biomethane strategy can contribute to a complete substitution of diesel fuel in urban buses and gives savings of around 1,000 tCO2/year. The price of the biomethane was found to be the most sensitive input factor. It is suggested that it should not exceed 0.40 EUR/Nm3 for a fuel conversion project of a fleet of 10 vehicles. Such a price can be ensured, if dry fermentation technology is chosen for biogas production. However, from the sustainability perspective, wet fermentation is more preferable due to the introduction of a source-separated organic waste management system in the region and higher gas yields. Introduction of this alternative requires additional funds which is a question of policy-level decisions.

Sustainable Use Of Macro-Algae For Biogas Production In Latvian Conditions: A Preliminary Study Through An Integrated Mca And Lca Approach

Abstract The study focuses on sustainability evaluation of an algae-based energy system in Latvia with a holistic and integrated approach of multi-criteria analysis combined with life cycle assessment (including a practical side - biogas yield experiments of locally available algae). The study shows potential for sustainable use of algae in Latvian conditions and thus that algal biomass can be utilized for the production of biogas. The most sustainable and feasible scenario of using algae for biogas energy production foresees the collection of algae biomass from natural water bodies. Important beneficial effects through the use of algae are related to avoiding global warming potential (GWP) and eutrophication impacts. Biogas batch experiments carried out with the local macrophyte C.demersum have shown a methane yield of 554 l CH4/kg VS.

Energy Recovery from End-of-Life Tyres: Untapped Possibility to Reduce CO2 Emissions

Energy Recovery from End-of-Life Tyres: Untapped Possibility to Reduce CO2 Emissions In this paper the possibility to reduce CO2 emissions by energy recovery from waste tyres is discussed. The objective of the study is to analyze the end-of-life tyre market in Latvia, to assess the amount of used tyres available and to calculate the potential reduction of CO2 emissions by energy recovery from tyres in mineral products industry. Calculation results show that an improved collection and combustion of end-of-life tyres in the cement industry can save up to 17% of the present CO2 emissions in the mineral products industry.

Evaluation of Biomass Availability for Biogas Production at Regional Level

Evaluation of Biomass Availability for Biogas Production at Regional Level Currently available data were used in an integrated deterministic modelling approach to assess the total biomass availability. The conceptual approach of combining the benefits of relational database and GIS modelling was tested in two eastern European countries - in Latvia and Romania, both located in different bio-geographical regions. The developed system has proven its efficiency in dealing with heterogeneity in different levels of complexity regarding environmental and ecological structures. The overall approach of assessing the biomass resources was first to estimate the quantity of material generated from municipal waste and agricultural practices in each of research areas. The quantity of material that could be recovered from these practices was then taken into account and the technical and environmental constraints associated with other site factors were evaluated. As a result, the particular areas with high, medium and low potential in each country were identified.