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Global resource limits and increasing demand for non-fossil energy sources have expanded the research on alternative fuels. Among them, algal biomass is designated as a third-generation feedstock with promising opportunities and the capability to be utilized for energy production in the long term. The paper presents the potential for converting beach wrack containing macroalgal biomass into gaseous fuel as a sustainable option for energy production, simultaneously improving the organic waste management that the coastline is facing. Beach wrack collected in the northern Baltic Sea region was converted by gasification technology applicable for carbon-based feedstock thermal recovery, resulting in syngas production as the main product and by-product biochar. Proximate and ultimate analysis, trace and major element quantification, detection of calorific values for macroalgal biomass, and derived biochar and syngas analysis were carried out. A higher heating value for beach wrack was estimated to be relatively low, 5.38 MJ/kg as received (or 14.70 MJ/kg on dry basis), but produced syngas that contained enough high content of CH4 (42%). Due to macroalgal biomass specifics (e.g., high moisture content and sand admixture), an adjusted gasification process, i.e., the combination of thermochemical procedures, such as mild combustion and pyrolytic biomass conversion, might be a better choice for the greater economic value of biowaste valorization.

A modern, environmentally friendly urban lifestyle requires paying attention to landscaping and green areas. The scarcity of free land in cities and the high price of land require the combination of greenery with buildings—both vertically and horizontally. The developed green technology for construction brings together computer numerical control (CNC) processing of supporting structures and prefabricated solid planting blocks made of concrete composite. The timber structures are fixed together using traditional carpentry joints. The details, which will be manufactured in the factory using CNC processing at a controlled temperature and humidity corresponding to indoor conditions, can be easily assembled on the construction site. The high bending strength but good elasticity and connections of carpentry joints endow the structure with good properties in a non-controllable environment. By combining CNC-processed wooden structures with concrete technology as substrate composites, labor-intensive manual work in landscaping and gardening will be reduced in the future. The novel material-hardening substrate composite material uses only the residues as the raw materials.

Agricultural activities can have several adverse impacts on the environment; such as important greenhouse gas (GHG) emissions. To implement effective mitigation measures and create effective policies, it is necessary to know the full carbon and nitrogen budgets of agro-ecosystems. However, very often, information regarding the pools or fluxes involved in the carbon and nitrogen cycles is limited, and essential complementary data needed for a proper interpretation is lacking.This study aimed to quantify all the relevant pools and fluxes of a winter rapeseed, a widely spread crop in the Europe and Baltic regions. The N2O and CH4 fluxes were measured weekly using the closed static chamber method from August 2016 to August 2017 in a winter rapeseed field in Central Estonia. Additionally, nutrient leaching and soil chemical parameters, as well as environmental parameters like soil moisture, electrical conductivity and temperature were monitored. At the end of the season, the rapeseed and weed biomasses were collected, weighed and analyzed. The remaining relevant fluxes in the N cycle were calculated using various non-empirical methods: NH3 volatilization was estimated from slurry and environmental parameters, N deposition and NOx emissions were obtained from national reports, and N2 emissions were calculated with the mass balance method. Regarding the C cycle, gross primary production (GPP) of the rapeseed field was also calculated by the mass balance method. Simultaneously, for comparison and validation purposes, GPP was estimated from the data provided by MOD17A2H v006 series from NASA, and N2 was estimated from the measured emissions of N2O using the N2:N2O ratio calculated from the DAYCENT model equations.N2 emissions and GPP were the biggest fluxes in the N and C cycles, respectively. N2 emissions were followed by N extracted with plant biomass in the N cycle, while in the carbon cycle soil and plant respiration and NPP were the highest fluxes after GPP. The carbon balance was positive at the soil level, with a net increase in soil carbon during the period, mainly due to GPP carbon capture. Contrarily, the nitrogen balance resulted in a net loss of N due to the losses related to gaseous emissions (N2 and N2O) and leaching.To conclude, it was possible to close the C and N budgets, despite the inherent difficulties of estimating the different C and N environmental pools and fluxes, and the uncertainties deriving from some of the fluxes estimations.

Composting is a sustainable method for recovering nutrients from various organic wastes, including food waste. Every input waste has different nutrient contents, in turn, suggesting that every compost has different fertilizer and/or soil improvement values. The phosphorus (P) concentration and relative distribution of P forms is related to the original organic material. The relative distribution of P forms determines how readily plants can absorb P from the compost-amended soil. The aim of this study was to investigate the content and relative share of P forms in composts made from fish waste, sewage sludge, green waste, and horse manure. Six forms of P (labile, bound to reducible metals, bound to non-reducible metals, bound to easily degradable organic material, and bound to calcium) were determined using sequential extraction method. The results indicated that fish waste compost had relatively high proportion of labile P, suggesting good biological availability. In comparison, sewage sludge compost contained the highest overall P concentration per dry weight unit, while labile P constituted only 6% of summary of P forms. The results indicate that the evaluation of composts as alternative P sources in agriculture should rely on the relative distribution of P forms in the compost in addition to the typically recognized value of the total P.

Implementation of construction works on weak (e.g., compressible, collapsible, expansive) soils such as peatlands often is limited by logistics of equipment and shortage of available and applicable materials. If preloading or floating roads on geogrid reinforcement or piled embankments cannot be implemented, then soil stabilization is needed. Sustainable soil stabilization in an environmentally friendly way is recommended instead of applying known conventional methods such as pure cementing or excavation and a single replacement of soils. Substitution of conventional material (cement) and primary raw material (lime) with secondary raw material (waste and byproducts from industries) corresponds to the Sustainable Development Goals set by the United Nations, preserves resources, saves energy, and reduces greenhouse gas emissions. Besides traditional material usage, soil stabilization is achievable through various secondary raw materials (listed according to their groups and subgroups): 1. thermally treated waste products: 1.1. ashes from agriculture production; 1.2. ashes from energy production; 1.3. ashes from various manufacturing; 1.4. ashes from waste processing; 1.5. high carbon content pyrolysis products; 2. untreated waste and new products made from secondary raw materials: 2.1. waste from municipal waste biological treatment and landfills; 2.2. waste from industries; 3. new products made from secondary raw materials: 3.1. composite materials. Efficient solutions in environmental engineering may eliminate excessive amounts of waste and support innovation in the circular economy for sustainable future.

Biochar has been proposed as an amendment that can improve soil conditions, increase harvest yield, and reduce N losses through NO3&minus, leaching and N2O emissions. We conducted an experiment to test the hay biochar mitigation effect on N2O emissions depending on its production temperature. The pot experiment consisted of the soil amendment with three different production temperature biochars (300 &deg, C, 550 &deg, C, 850 &deg, C) alone and in combination with three different organic fertilizers (cattle slurry, slurry digestate, vinasse), in growth chamber conditions. The effects of biochar and fertilizer were both significant, but the interaction biochar:fertilizer was not. The amendment with the three fertilizer types and with the highest production temperature biochar resulted in significantly higher cumulative N2O fluxes. Biochar did not show a mitigation effect on N2O emissions when applied with organic fertilizer. Cumulative emissions were higher with biochar addition, with increasing emissions for increasing biochar production temperature. Our results support the idea that biochar cannot be considered as a universal tool for the reduction of N2O emissions.

Construction of road embankments in peatlands commonly involves replacement of the peat with a fill-up soil of an adequate load-bearing capacity. This usually requires a lowering of the water level, turning a peatland from a carbon sink to a source of greenhouse gases. Thus, alternatives are sought that are less costly in both economic and ecological terms. Mass-stabilization technology can provide a cheap substitute for Portland cement. Calcareous ashes (waste materials), supplemented with pozzolanic and alkali additives to facilitate and accelerate the setting and hardening processes, are attractive alternatives to soil excavation or replacement techniques. Silica fume and waterglass were used as pozzolanic agents and KOH as a soil-alkalizing agent. X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analyses and stress–strain tests were performed for the hardened samples. Crystallization of alkali feldspars was observed in all test samples. Comparable hardening of peat soil was achieved for both ashes. It was shown that the ashes of Estonian kukersite (oil shale) from both pulverized firing and a circulating fluidized bed incineration process (produced in energy sector as quantitatively major solid waste in Estonia) can be used as binding agents for peat stabilization, even without the addition of Portland cement. Hardened peat soil samples behaved as a ductile material, and the cellulose fibers naturally present in peat gave the peat–ash composite plasticity, acting mechanically in the same way as the steel or glass fiber in ordinary reinforced concrete. The effect of peat fiber reinforcement was higher in cases of higher load and displacement of the composite, making the material usable in ecological constructions.

The current study estimated (i) the effect of mineral N fertiliser (NH4NO3), municipal sewage sludge and cattle slurry on hemp cultivar (cv) USO-31 and sunflower cv Wielkopolski above ground biomass yield, (ii) the efficiency of nitrogen recovery of the applied amendments (nitrogen recovery, %), nitrogen use efficiency (NUE, kg kg −1 ) and the profitability (%) of briquette production from hemp and sunflower above ground biomass. A long-term field trial was established in 2008–2011 at Estonian University of Life Sciences (5823′N, 2644′E) on Stagnic Luvisol soil (sandy loam surface texture, C 1.12%, and N 0.12%, pH KCl 5.6). The plants were grown on different N treatments: N 0 (without N), N 100 (mineral N fertiliser NH 4 NO 3 ), sewage sludge from the city of Tartu, and cattle slurry. The applied amount of N for all treatments (with the exception of the N 0 treatment) was 100 kg N ha −1 . The energy sunflower has high potential to produce vigorous above ground biomass in north European conditions. But, it is necessary to continue the field trials with this crop to clarify the biomass yield stability over many years. In point of profitability, the sewage sludge could be used as organic fertiliser for energy crops, because the biomass increase by 1 kg of sludge N was the highest and biomass yield over trial years more stable of the fertilisers tested. In most years 100 kg N ha −1 did not guarantee profitable above ground biomass production of hemp in low fertility soil. Cattle slurry for energy crops with slow initial development is not a promising organic fertiliser.

The effect of returning turfgrass clippings on mown turf, in terms of the value of clippings as a nitrogen source as well as management interactions on grass growth, has not been well examined. The objective of the present research was to study the impact of N rate and weather during the growing season on the effect of returned clippings and on efficiency of returned clippings. The experiment was carried out between 2004 and 2008. Over a five-year period, a field experiment was conducted on a sward of Festuca rubra rubra and Poa pratensis. Measured experimental factors included two clipping treatments, with clippings removed or clippings returned, as well as seven fertilizer rates.The swards' dry matter yield was significantly influenced by clippings treatment, applied N rate, year, and these interactions. Returning turfgrass clippings provide significant positive effects on the dry matter yield only when plants are fertilized with N. Without N fertilization, the effect was negative or absent. Returned cl...

Reed canary grass is a potential bio-energy crop in Northern Europe. As plantation biomass production depends on local pedoclimatic conditions, it is important to evaluate yield in the context of soil-specific characteristics. The current study used regression models to evaluate reed canary grass yield variability in the context of soil nitrogen (N) content and in applied mineral N fertilisers. Reed canary grass bio-energy potential was evaluated in a soil-specific manner to calculate the production and energy use efficiency. Soils with low N content produce yields of almost 1 Mg ha−1 in years with unsuitable weather conditions for plant growth. The average dry matter yield of 6–7 Mg ha−1 is achievable within limited years on soils with N contents of more than 0.6%. Fertilisation increases the yield and decreases yield variability in humus-poor soils, but on soils with high N content, production risks increase with increasing N fertiliser applications. Energy use efficiency decreases with increasing input on Histosols; increasing the input from 6 to 31 GJ ha−1 results in energy use efficiency decreasing from 9 to 2 GJ GJ−1. As a consequence of energy use efficiency, a diminishing return occurs on Haplic Albeluvisol, as optimum efficiency peaks at 5.2 GJ GJ−1 using 198 kg N ha−1. The current study integrated the developed models in the soil Geographic Information System and calculated the energy use efficiency of selected areas. This approach enables researchers to evaluate production risks in the region and provides a framework for knowledge-based bio-energy production.

Impact of soil management practices on the abundance and diversity of the soil earthworm community This work was funded by the European Commission Horizon 2020 project SoildiverAgro [grant agreement 817819].

Ecological groups of earthworms This work was funded by the European Commission Horizon 2020 project SoildiverAgro [grant agreement 817819].