This study evaluates the environmental impact assessment of sustainable pig farm via management of nutrient and co-product flows in the farm. Manure management and biogas production are among the most promising pathways towards fully utilizing organic waste within a circular bioeconomy as the most environmentally friendly solution mitigating gaseous emissions and producing bioenergy and high-quality bio-fertilizers. The concept of farm management includes rearing pig, growing all the feeds needed, and managing the nutrients and co-product flows in the farm. A consequential life cycle assessment (LCA) was performed to examine three scenarios in which all the generated manure is used as fertilizer for barley cultivation and mineral fertilizer is used where necessary (SC1); produced surplus straw is used for thermal energy generation and maize is used for sale, substituting maize biomass in the market (SC2); and all co-products are circulated in a closed system (SC3). The functional unit (FU) was defined as a “farm with 1000 fattening pigs at farm gate”. The analysis showed that heat generation from wheat, barley and legumes straw has a significantly higher positive environmental impact than the use of these cereal straw for biogas production. The partial replacement of mineral fertilizers with digestate has positive environmental effects in terms of abiotic depletion, photochemical oxidation, terrestrial ecotoxicity, freshwater aquatic ecotoxicity, human toxicity, and marine aquatic ecotoxic aspects. The amount of digestate generated on a farm is not sufficient to completely eliminate the use of mineral fertilizers for plant fertilization. The generated pig manure (SC1) and digestate (SC2) is only enough for the fertilization of 8.3% of the total cultivated land of farm applying 22.9 t/ha rate.
Recovery of nutrients from biomass combustion ash is of great importance for sustainable bioenergy waste use. In this work, granulated fertilizer materials were engineered from biofuel bottom ash, lime kiln dust and water, analysed for their chemical complexity and tested in pot experiments (2017–2018) for their propensity to release nutrients. The results obtained in this work showed that spring barley yield was observed to be the highest for granulated biomass ash with 30% of ash in the granule. The yield increased 3.99 t ha−1 per 100 kg ha−1 potassium oxide (K2O) in 2017 and 1.23 t ha−1 per 100 kg ha−1 K2O in 2018. Straw yield varied between 1.39–5.08 t ha−1/100 kg ha−1 in 2017 and 0.36–1.23 t ha−1/100 kg ha−1 in 2018. Calcium concentration significantly increased in soil. No significant changes in soil mobile phosphorus (P) were obtained as well as for the heavy metal concentrations in soil. This suggests that biofuel ash can be a significant source of certain major nutrients for crops that can also beneficially affect soil pH. The results of this work can provide policy-makers with the information needed to diversify existing and enable new biomass bottom ash utilization routes which currently vary significantly between the countries.
The race is on to achieve an important level of efficiency in the attainment of a circular economy in agriculture especially with the aim of sustainable nitrogen management. This cycle in the agricultural sector cuts across livestock farming, agriculture-induced waste generation, recycling and utilization, energy generation, crop production, ecosystem protection and environmental management through the mitigation of climate changes. In this work, we assess the process and functionalities of livestock waste generated from the piggery farm and their combinations with other by-products such as biochar and ash in comparison with mineral fertilization as sources of nitrogen applied in agricultural soil. The experiment was performed in a controlled environment with wheat ( Triticum aestivum L.) grown in a neutral and an acidic soil. Pig manure was used as the primary feedstock, fed and processed to biogas and nutrient-rich digestate by the anaerobic digestion process. The results revealed that the co-amendments of pig manure digestate with biochar and ash had complimentary positive effect on measured indices such as mobile potassium, phosphorus, biomass yield and nitrogen use efficiency. The mineral nitrogen fertilizer significantly induced carbon dioxide emissions from day 35 when compared to emissions from the organic amendments. In contrast, the organic amendments influenced nitrous oxide emissions from the onset till day 30 before flattening out. The individual combination of pig manure digestate with biochar and ash had a negative influence on enzymatic activity (dehydrogenase). Soil microbial biomass carbon was induced across all treatments in both soil types. Pig manure digestate + ash and pig manure digestate had 32.1 and 48.8% soil microbial biomass increase in neutral soil and acidic soil, respectively. Overall, the processing and application of single-use amendment or in combination with biochar and ash holds huge potential in the optimization of nitrogen and carbon efficiency towards sustainable soil management via improving soil quality, carbon sequestration and climate change.
Biofuel production and bioenergy generation play significant role in the energy self-sufficiency of the countries, climate change mitigation, but also increase the accumulation of waste. The main waste of biomass burning process is ash and lime kiln dust. This study hypothesized that those materials could be potential fertilisers for agricultural crops. The aim of the research was to evaluate the uptake of nutrients in spring barley grain and straw when using granulated ash and bulk biofuel ash in an open-air pot experiment. The results obtained in pot experiment showed that using granulated ash an increase of total potassium (K tot) content (21.5-28.0 g kg-1) in spring barley straw was observed in 2018, while in 2017 the amount of K tot did not change significantly. Calcium concentration in straw increased significantly in the second year of the experiment. No significant changes in the content of heavy metals (Cd, Pb, Ni and Cr) were observed in the soil. The concentrations of these metals did not exceed the permissible levels. Due to the high Cu and Zn concentration in biofuel ash, the content of these microelements increased in the soil. Overall, the content of major nutrients, microelements and heavy metals increased with increasing biofuel ash content in granules: in spring barley grain, Cd (0.003-0.030 mg kg-1) and Zn (4.58-22.5 mg kg-1) were detected, in straw-Zn and Cu.
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