Mechanical Properties of Alkali Activated Material Based on Red Clay and Silica Gel Precursor

The search for alternative alumosilicates source for production of alkali activated materials (AAM) is intensively researched. Wide spread of natural materials such as clays and waste materials are one of potential alternatives. In this research AAM was made from local waste brick made of red clay and calcined low-carbonate illite clay precursor and its properties evaluated. Waste silica gel containing amorphous silica from fertilizer production plant was proposed as additional raw material. 6 M and 7 M NaOH alkali activation solutions were used to obtain AAM. Raw materials were characterized by X-ray diffraction, laser particle size analyser, DTA/TG. Raw illite clay was calcined at a temperature of 700 to 800 °C. Waste brick was ground similar as raw clay and powder was obtained. Replacement of red clay with silica gel from 2–50 wt.% in mixture composition was evaluated. Results indicate that the most effective activator was 6 M NaOH solution and AAM with strength up to 13 MPa was obtained. Ground brick had the highest strength results and compressive strength of AAM reached 25 MPa. Silica gel in small quantities had little effect of AAM strength while significant strength reduction was observed with the increase silica gel content. The efflorescence was observed for samples with silica gel.

Capture, Storage and Utilization of Carbon Dioxide by Microalgae and Production of Biomaterials

Carbon dioxide emissions are strongly related to climate change and increase of global temperature. Whilst a complete change in producing materials and energy and in traffic and transportation systems is already in progress and circular economy concepts are on working, Carbon Capture and Storage (CCS) and Carbon Capture and Utilisation (CCU) represent technically practicable operative strategies. Both technologies have main challenges related to high costs, so that further advanced research is required to obtain feasible options. In this article, the focus is mainly on CCU using microalgae that are able to use CO2 as building block for value-added products such as biofuels, EPS (Extracellular Polymeric Substances), biomaterials and electricity. The results of three strains (UTEX 90, CC 2656, and CC 1010) of the microalgal organism Chlamydomonas reinhardtii are discussed. The results about ideal culture conditions suggest incubation temperature of 30 °C, pH between 6.5 and 7.0, concentrations of acetate between 1.6 and 2.3 g L–1 and of ammonium chloride between 0.1 and 0.5 g L–1, the addition of glucose This green microalga is a valid model system to optimize the production of biomass, carbohydrates and lipids.

Is It Possible to Obtain More Energy from Solar DH Field? Interpretation of Solar DH System Data

Europe has a course to zero emissions by 2050, with a strong emphasis on energy sector. Due to climatic conditions in Latvia, district heating (DH) plays an important role in the energy sector. One of the solutions to achieve the set goals in DH is to introduce emission-free technology. Therefore, the popularity of installation of large-scale solar collector plants continues to increase in DH in Europe. The first large-scale solar collector field in the Baltic States was installed in 2019. Solar collector active area is 21 672 m2 with heat storage water tank 8000 m3. The article shows the first operation results of this system and evaluates influencing factors. The results of the analysis show that system productivity is mainly demanded by solar radiation, and the strongest correlation between these parameters were established in May. The highest correlation between ambient air temperature and produced thermal energy is reached when ambient air temperature is between 7 °C to 15 °C and production process has not been externally regulated. The temperature difference between flow and return temperatures of the heat carrier affect solar collector performance minimally and strong correlation was not observed.

Industrial Wastewaters of the Feed Industry: use of Sodium Ferrate in the Phenol Purification Process

The article presents the results of studies of the possibility of using sodium ferrate in the treatment of wastewater from organic substances on the example of phenol in the production of combined feed. This research has shown the technology of obtaining encapsulated ferrate using hexane, ethylcellulose and paraffin; it has also established the stability of encapsulated sodium ferrate in air and in an alkaline solution. Furthermore, the evaluation of the efficiency of using encapsulated sodium ferrate in the purification of the simulated solution from phenol in the technology of combined feed production.

Valorization Methodology for Agriculture Sector Climate Change Mitigation Measures

Agriculture sector holds an essential role in Latvia’s economy and play significant role in keeping rural areas as a habitable environment (approximately 32 % of the population lives in rural areas). The agricultural sector is responsible for 28.5 % (2018) of total non-European Union Emissions Trading System (non – EU ETS) greenhouse gas (GHG) emissions in Latvia. The largest part of emissions is related to agricultural soils (59.3 %) and enteric fermentation 32.6 % (mainly dairy and beef cattle). The GHG emissions trend of recent years shows a gradual and steady increase in GHG emissions for example between 2005 and 2018 +12.5 % and during the period 2013–2018 emissions increased by 2.12 %. According to Latvia’s National Energy and Climate Plan 2021–2030 (NECP), total GHG emissions in the agricultural sector are expected to increase in the period from 2020 to 2030, mainly in the enteric fermentation and agricultural soil categories. To achieve determined targets for Latvia’s non-EU ETS sector in 2030 and be on track to reach climate neutrality in 2050, the agricultural sector has to contribute to GHG emission mitigation. For the agricultural sector, improved food security and climate smart activities will be necessary to achieve GHG emission reduction. Existing policies and measures (WEM) as well as those which are included in the NECP as additional measures (WAM) were used to assess more suitable measures to move on climate smart agriculture (CSA), that could help to decrease GHG emissions at the farm and state level as well as is expected to contribute towards achieving the commitments in the plan. To achieve the aim of the study, a combination of the Delphi method together with multi-criteria analysis (MCA) is utilized to find a set of top GHG mitigation measures in the future. Results show that, in the future, the measure support the development of innovative technologies and solutions to promote resource efficiency in agriculture is essential to move on climate smart agriculture.

Temporal Trends in Phosphorus Concentrations and Losses from Agricultural Monitoring Sites in Latvia

The Baltic Sea is the youngest sea on our planet, the environment of the sea is considered to be unique and fragile. It is affected by various human activities resulting in the impairment of water quality. Riverine nutrient (nitrogen and phosphorus) loads are among the major causes of eutrophication of the Baltic Sea. This study examines temporal trends in water discharge, total phosphorus (TP) and orthophosphate-phosphorus (PO4-P) concentrations and losses from three agricultural runoff monitoring sites in Latvia including Berze, Mellupite, and Vienziemite. The annual datasets of TP and PO4-P concentrations and losses were tested for statistical trends using a nonparametric test - the Mann-Kendall trend test. The timeframe of this study was from 1995 until 2018. The results show a large variety of annual mean concentrations and losses of TP and PO4-P in the study period. No statistically significant trend was detected for TP losses. Meanwhile, statistically significant downward trends were observed for TP concentrations in four out of six study sites and in two study sites for PO4-P concentrations.

Electronic Waste Generation Prediction in Bandung City, Indonesia

Nowadays waste electrical and electronic equipment (WEEE) generation is increasing due to the increase in the number of users and the development of electronic products. In Indonesia, there are no specific regulations about WEEE even though it is identified as hazardous and toxic waste. This study aims to predict the WEEE generation from the most used and replaced electronic products by citizens of Bandung City. The data is collected by surveying 400 families in Bandung City. Based on the survey results, there are three types of electronic products that are most used and replaced by citizens of Bandung City, which are mobile phones, laptops and televisions. The Delay Model is modified by replacing the lifespan variable with end-of-life to project the mobile phones, laptops and televisions waste generation in Bandung City. The purpose of this modification is to adjust the pattern of electronic products used in developing countries. The projection results state that Bandung City will generate 0.61 tons/day of mobile phones, 8.66 tons/day of laptops and 3.16 tons/day of televisions at the end of 2020. Based on the results of the projection, WEEE management and recycling is important which can reduce WEEE disposal and increase the economic value of WEEE.

How to Assess Policy Impact in National Energy and Climate Plans

It is the responsibility of each member state of the European Union, to prepare a national energy and climate plan and set achievable climate targets and meaningful measures and policies to achieve the targets set. Annex 4 of the Latvian National Energy and Climate Plan for 2030 (hereinafter – NECP) provides an overview of policies and measures to achieve the climate targets. The NECP does not provide information on the impact of the policies or which measures are more important and which are less crucial Similarly, the measures in Annex 4 of the NECP were not determined by industry experts but by ministry officials, therefore, it is not clear whether the proposed measures will achieve the set climate targets, a point also made by European Commission in its evaluation report on NECP. The aim of the study is to develop a tool for the early assessment of the impact of energy and climate policy measures. The study developed a methodology to pre-assess the impacts of the policies identified in the NECP, impacts were described by measures effectiveness and stage of development. With this methodology, it is possible to assess the impact of energy policies using indicators to characterize the effectiveness of the policy and the level of development. The study confirmed that both the multi-criteria analysis and composite index method can be used as methods. The results showed that high impact measures were related to the promotion of energy efficiency in buildings, but low impact measures were comprehensive horizontal measures such as measures related principle ‘energy efficiency first’ and review of energy efficiency obligation schemes. The indicators with the highest impact on sustainability rate were possible side effects and transparency of policies.

Complete Circularity in Cross-Laminated Timber Production

Many authors have discussed the paradigm shift in economy from linear to circular. Population growth and climate change caused resource scarcity are the main driving forces of shifting to circularity approach. Although consumers have been slower regarding transitioning to more sustainable economy, production companies are the ones who have felt the scarcity of resources first. In this paper we are exploring cross-laminated timber (CLT) production residue utilization possibilities for new product production and using multi-criteria analysis calculating the most promising recycling alternative from the perspective of companies working with wood as raw material. Data matrix for multi-criteria analysis was constructed from literature analysis gathering data on five criteria: (1) production costs; (2) energy consumption; (3) CO2 emissions; (4) product market price and (5) final product to wood residues ratio. Multi-criteria analysis showed that production of mycelium insulation material is the most promising alternative for CLT production residue recycling.

Investigation on Relative Heat Losses and Gains of Heating and Cooling Networks

The integration of district heating (DH) and cooling (DC) in the sustainable energy system of the future requires a significant reduction in operating temperatures. Supply temperatures below 70 °C are required for new 4th Generation DH. Main benefits are the use of low exergy heat sources and the reduction of heat losses. The reduction of heat losses is achieved by reducing the driving temperature difference between the medium pipe and the ground. The decrease of the return temperature level is limited by the consumer behaviour and the ground temperature level. As a consequence, the reduction of the supply temperature is accompanied by a reduction of the maximum transmittable heat flow. For energy efficiency and economic reasons, the relative heat losses are therefore an important design value for DH networks. The study proposes an approach to estimate the relative heat losses by using steady-state heat loss models and analyses the values for different DH generations. In particular, due to the rising of the near-surface soil temperature, the relative cold losses are also studied.