Microalgae biomass as a renewable biostimulant: meat processing industry effluent treatment, soil health improvement, and plant growth

Soil health improvement by inoculation of indigenous microalgae in saline soil

Using biological methods to improve saline soils is recognized as an eco-friendly and sustainable way. In this study, two indigenous algae YJ-1 and YJ-2 screened from salinized farmland were inoculated into saline soils with different salinization levels to investigate their potential in enhancing soil health by laboratory microcosm experiment. The results showed that individual inoculation of the two algae quickly resulted in the formation of algal crusts, and the chlorophyll content in the saline soils gradually increased with the incubation time. The soil pH decreased significantly from the initial 8.15-9.45 to 6.97-7.56 after 60-day incubation. The exopolysaccharides secretion and the activities of catalase, sucrase, and urease in saline soils also increased. Microalgal inoculation increased soil organic matter storage, while decreasing the available nutrient contents possibly due to the depletion of microalgal growth. PCA and PCC results identified that microalgal biomass as the predominant variable affecting soil quality. Overall, these data revealed the great potential of microalgae in the amelioration of saline soils, especially in pH reduction and enzyme activity enhancement. This study will provide the theoretical foundation for improving saline soils via algalization.

Soil and Foliar Applications of Wood Distillate Differently Affect Soil Properties and Field Bean Traits in Preliminary Field Tests

Natural products such as wood distillate (WD) are promising alternatives to xenobiotic products in conventional agriculture and are necessary in organic farming. A field study gave insight into the effectiveness of WD applied as foliar spray (F-WD), soil irrigation (S-WD), and their combination as growth promoters for field beans. The soil fertility and quality parameters, plant growth, nutrient uptake, and resource partitioning within plants were evaluated. In a pot trial, we tested the effect of S-WD on root nodule initiation and growth. S-WD increased DOC and microbial biomass by approximately 10%, prompted enzyme activities, and increased nitrate and available phosphorus in soil, without affecting the number and growth of nodules in field beans. In contrast, the F-WD slightly reduced the DOC, exerted a lower stimulation on soil enzymes, and lowered the soil effect in the combined distribution. In field beans, the F-WD reduced the stem height but increased the number of pods per stem; S-WD increased the N and P concentrations of leaves and the N concentration of the pods. Moreover, all WD treatments retarded plant senescence. The WD revealed itself to be promising as a growth promoter for grain legumes, but further research is needed to understand the interference between the combined soil and foliar applications.

Pyrolysis of Biosolids to Produce Biochars: A Review

The continuing increase in population means an increasing demand for products and services, resulting in huge amounts of waste being discharged into the environment. Therefore, waste management requires the application of new and innovative solutions. One new approach involves converting waste into value-added chemicals and products for use directly or after further processing into higher value-added products. These processes include biological, thermochemical, and physiochemical methods. Furthermore, biosolids, including treated sewage sludge (SS), represent one of the major by-products of human activities, constituting a major environmental hazard and requiring the treatment of contaminated wastewater with associated health hazards. Sustainable solutions to manage and dispose of this type of waste are required. In this review, pyrolysis, a thermochemical conversion technology, is explored to convert biosolids to biochars. The review addresses previous studies, by providing a critical discussion on the present status of biosolids processing, the potential for energy recovery from the pyrolysis bio-oil and biogas, and finally some benefits of the production of biochars from biosolids.