Up to now, primary resources have been the main choice of raw material selection for production. Now, global market tendencies have brought significant attention to secondary resources as the price has been raised for primary materials, and there is a shortage of their delivery. This could bring an additional effort to increase the recycling level of construction and demolition waste, including expanded polystyrene (EPS). Efforts have been made to develop new efficient building materials with a high content of recycled EPS. In this paper, composite insulation material made of gypsum hemihydrate and recycled EPS beads by casting and compression methods were evaluated, and properties were compared. Thermal and sound insulation properties were characterized. Density from 48 to 793 kg/m³ was obtained and the thermal conductivity coefficient from 0.039 to 0.246 W/(m·K) was measured. Compression strength was from 18 kPa to 2.5 MPa. Composites produced with the compression method have a sound absorption coefficient α > 0.9 in the range from 600 to 700 Hz, while the samples produced by casting showed poor sound absorption with wide deviation. Compression methods had an advantage over the casting method as more homogenous and lightweight materials were produced with improved insulation properties.

Cement is a widely used building material, with more than 4.4 billion metric tons produced in 2021. Unfortunately, the excessive use of cement raises several environmental issues, one of which is the massive amounts of CO_2e produced as a by-product. Using recycled materials in the concrete mix is widely employed to solve this problem. A method for minimizing the use of natural cement by substituting it with secondary cementitious material that consists of wood–cement board manufacturing waste has been studied in this paper. The cement in the waste stream was reactivated by a mechanical treatment method—the use of a planetary mill, allowing it to regain its cementitious properties and be used as a binder. Physical and mineralogical analysis of the binder material was performed using X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA) and Brunauer–Emmett–Teller analysis; granulometry and compressive strength tests were also carried out. The results show that the grinding process did not significantly change the mineralogical composition and the specific surface area; it did, however, affect the compressive strength of the samples prepared by using the reactivated binding material; also, the addition of plasticizer to the mix increased compressive strength by 2.5 times. Samples were cured in high-humidity conditions. The optimal water-to-binder (W/B) ratio was found to be 0.7 because of the wood particles that absorb water in their structure. Compressive strength increased as the grinding time increased.

Over the last decade, research has increasingly focused on reducing the use of natural resources and improving waste management in the construction industry. Various possibilities exist for reducing waste in this sector, ranging from using waste as filler materials to developing new binders and building materials. This study focuses on the development of bio-based building materials using waste from the manufacturing of wood-wool cement boards. The binder and filler materials were obtained from the manufacturing waste and used in this research. The developed materials were tested for their visual appearance, macrostructure, material density, thermal conductivity coefficient and compressive strength. The results showed promising data for the self-bearing bio-based building materials, which had similar thermal properties to other bio-based materials and could be used as thermal insulation materials with a thermal conductivity coefficient of 0.0827–0.1172 W/(mK). The material density of the developed bio-based composites was found to be 430–617 kg/m³. By incorporating manufacturing waste into the production process of bio-based building materials, it becomes evident that overall waste from manufacturing plants can be significantly reduced, and the sustainability aspect of wood-cement board manufacturers can be enhanced.

The construction and demolition waste recycling into secondary raw materials is vital to achieving a sustainable and circular building life cycle. Expanded polystyrene (EPS) is one of the materials whose recycling rate should be increased. EPS boards can be shredded and used as aggregate of lightweight cement composites resulting in a material with combined properties subjected from EPS and mineral binder. To reduce the open structure of shredded EPS particles, proper treatment could improve EPS performance. The heat treatment of the aggregates can reduce the volume and increase their density. In this paper, EPS aggregates were heat-treated at 120 and 130 °C, and heat-modified EPS aggregates with a bulk density of 40 and 100 kg/m³ were incorporated as filler material in gypsum composites. The composites’ density, compressive strength, thermal conductivity, and sound absorption were characterized. Results indicate that a composite with a compressive strength from 15 to 136 kPa and a material density ranging from 48 to 194 kg/m³ can be obtained. Thermal conductivity was achieved from 0.0390 to 0.0604 W/(mK). Following the ISO 10534-2 standard, the noise reduction coefficient was determined and showed promising results at 600 to 800 Hz, reaching a sound absorption coefficient of 0.88.

A major problem in the modern world is the overuse of fossil resources. The use of such resources and of that amount contribute negatively to the environment we live in. Fossil resources should be replaced with renewable ones. That way, less impact would be done to the environment. Renewable resources would greatly contribute to a healthy sustainable future. Latvia currently ranks seventh on the number of biogas plants per 1 million per capita (27) and is searching for new ways and opportunities to switch from the production of electricity to biomethane. Thus, in this study, a mathematical approach for the calculations of biomethane potentials and emissions of different feedstocks under the anaerobic digestion principle was studied. Databases were searched for the factual numbers of livestock animals, as well as processed sludge, and average food waste. RED II and JEC Well-To-Wheels report v5 were analyzed for data on emission factors and future obligations. Out of combined biomethane potentials of different feedstocks, livestock manure’s potential share was 91%, of which 61% is dairy cow manure. The overall biomethane potential in Latvia is 2.21 to 4.28 PJ. Replacing fossil fuels with biomethane in the transport sector could lower the overall CO_2-eq emissions by 12.47–23.86% or 0.4–0.8 million tonnes.

More than 4.4 billion metric tons of cement were produced in 2021 [1], making it one of the most common building materials. Unfortunately, excessive cement use brings up several environmental concerns, one being the enormous volumes of CO_2e (carbon dioxide equivalent) created as a by-product. CO_2e is a standard unit for measuring carbon footprint and can be calculated for all greenhouse gases using global warming potential. Reducing CO₂ and other greenhouse gas emissions is crucial in modern cement manufacturing, as 0.9 kg of CO_2e is produced for every kg of cement. Cement manufacturing contributed by releasing 3.96 Gt of CO_2e into the atmosphere in 2021. This issue is often remedied using recycled materials in the fresh concrete mix as supplementary or pozzolanic additives. Some researchers have focused on regaining the activity of hydrated cement paste by grinding and thermally activating it [2–5], but a low-strength binder would also work for many applications. A low-strength binder recovered with as little energy as possible (only grinding, no heat treatment) could be considered a more sustainable and less energy-intensive way of recovery of the cement binder matrix. This study investigated a technique for recycling hydrated cement paste by mechanical treatment to disintegrate the hydrated cement conglomerate to reveal the unhydrated cement particles [6] that can be used as a recovered cementitious binder from processing waste from the production of wood-cement boards. Processing waste is defined as cement particles containing hydrated and unhydrated cement [7] and spruce wood fibres. The partly hydrated cement in the waste stream was mechanically processed in a planetary mill to reactivate it and restore its cementitious characteristics. The binder was characterized by density and mechanical compressive strength.