Search

Sewage sludge reuse in agriculture is increasing and is highly encouraged; however, it may pose environmental risk. Therefore, an integrated approach combining soil phytoremediation and further plant usage for bioenergy production is needed. In this study, we have examined the potential of industrial hemp (Canabis sativa L.) to remediate sewage sludge (SS) and sewage sludge char (SSCh)-amended soil (25–200 Mg ha−1) and improve soil quality. Additionally, hemp's biomass and probable bioenergy yield was calculated for biomass and methane production. Heavy metal soil content increased with SS and SSCh dose, though hemp cultivation significantly reduced their soil concentrations. The heavy metals' removal efficiency could be ranked Zn > Cu > Cr > Ni. There was an enrichment of micro- (Ca, Mg, Mn, S) and macro-nutrients (P) in SS and SSCh-amended soils. P and S removal by hemp was highly efficient, whereas other macronutrients did not show a substantial decrease in the soil. Only marginal removal was detected for Ba, Fe, Na, Ti and Al. The study showed that the optimal fertilization with SS or SSCh could be up to 25 Mg ha−1, when the highest efficiency of contaminant removal from the soil and the highest plant biomass production and bioenergy production were observed. [ABSTRACT FROM AUTHOR]

• Hemp biomass production on clay loam soil on average latitudes. • Heavy metal, alkaline earth-alkali metals and non metals distribution in hemp parts. • Bioconcentration factor impact to soil remediation of heavy metals. • Alkaline earth-alkaline metals and non metals impact to slagging process in combustion. Industrial hemp (Cannabis sativa L.) has emerged as a potential multipiurpose crop: fibre crop, energy crop, and phytoextractor of pollutants from the soil. However, the multipurpise grwoth of hemp was restricted as its cultivation in EU was legalized only in the past two decades. Most scientific researches of sewage sludge (SS) describe it at relatively low application levels for cultivation of different crops. Such lack of information requires a wide range of practices for fertilizing hemp with high level of sewage sludge or sewage sludge char (SSCh) doses. At this moment there are no guidelines for sewage sludge char fertilization of energetic plants, depending on soil type. The aim of the study was to analyze and compare SS and SSCh soil application effect on industrial hemp (Cannabis sativa L.) growth performance, and heavy metals accumulation to determine optimum SS or SSCh application rates for the growth of hemp. The experimental design consisted of four treatments: 1–25; 2–50; 3–100; 4–200 of sewage sludge and sewage sludge char Mg ha−1, and control soil (clay loam). It was determined that hemp ability to accumulate heavy metals depending on fertilisation intensity of sewage sludge and sewage sludge char decreased in all parts. Heavy metal distribution of hemp was selective; therefore their contents were decreasing in the following order: roots > stems > leaves. The study has confirmed the nutritional value of SS and SSCh. The potential of using the sewage sludge and its char as a source of organic matter for improvement of clay loam soil and a reasonable production of bioenergy crop like hemp without the use of inorganic fertilizers was shown. [ABSTRACT FROM AUTHOR]

Sewage sludge reuse in agriculture is increasing, however it can be an important route for contaminants to enter the environment. The aim of this study was to evaluate earthworm Eisenia fetida capability to reduce heavy metal content in the sewage sludge (SS) amended soil and increase soil fertility in terms of soil nutrients content. Adult earthworms were introduced into aged SS amended soil (0–200 Mg ha-1) and left for 65 days. Earthworms have stabilized soil pH and accelerated organic matter mineralization. The concentrations of most heavy metals during the vermiremediation sharply decreased, K and Mg decreased to a moderate extent, whereas Ca content has increased. The highest removal efficiency was detected for Ni, Co and Mn (> 80%), bioconcentration factors were as follows Zn > Co > Cu > Ni > Mn > Cr. The content of major nutrients (S, P) was substantially higher compared to the initial values. The most efficient remediation and soil quality improvement was achieved under the doses of 25–50 Mg ha-1. Higher (≥ 100 Mg ha-1) doses might restrict this technique application because of earthworm mortality and retarded growth. Overall, the study shows that vermiremediation might be a sustainable technique for ecological stabilization of SS amended soil and converting to usable for agricultural needs. [Display omitted] • Earthworms reduced toxic metals soil content and increased soil fertility. • Highest vermiremediation efficiency was in soils of low-moderate SS fertilization. • Vermiremediation is limited under high SS load due to impaired earthworm performance. [ABSTRACT FROM AUTHOR]