In the European Union (EU), the major N and P sources in agriculture are synthetic fertilizers although inputs from animal manure remain important, especially in regions of high livestock density. The use of synthetic fertilizers has dramatically increased food production worldwide, but the unintended costs to the environment and human health due to surplus and inefficient application have also been substantial. Thus, alternatives are needed. One of those represents the valorization of organic waste, the amount of which increased exponentially during the last decades. Its estimated annual increase is around 25 million tons [1].A major source of organic waste is sewage sludge (SS). Containing high amounts of N, with a median of 3.3% [2], P and OM, this material offers an excellent feedstock for the production of soil amendments that can reduce the need of synthetic P and N fertilizer [3,4]. At the same time it may increase the C-sequestration potential of cropped soils. In addition, sludge recycling as fertilizer or organic amendment helps to reduce the amount of organic waste by returning it into the bio-cycle while at the same time soil physical and chemical properties are restored [5,6]. Indeed, the Sewage Sludge Directive [7] and the working document on sludge [8] describe the use of SS on soils as beneficial but also seek to encourage a safe use of this material in agriculture and to regulate its application to prevent harmful effects on soil, vegetation, animals and humans [9]. Thus, in order to enable the use of SS as soil application, it first has to be decontaminated by removing organic pollutants and pathogen bacteria. Different treatments can be used for the latter: thermal drying, anaerobic digestion, conditioning with lime, etc. In general, the process of removing pathogen bacteria of SS is called hygienization. Heavy metals content also need to be taken into account. In cases their concentrations are above the allowed thresholds, strategies have to be developed to avoid secondary contamination due to SS application.Hydrothermal carbonization and pyrolysis of sewage sludges: wWhat happen to carbon and nitrogen? M. Paneque a, ⁎
Peat is used as a high quality substrate for growing media in horticulture. However, unsustainable peat extraction damages peatland ecosystems, which disappeared to a large extent in Central and South Europe. Furthermore, disturbed peatlands are becoming a source of greenhouse gases due to drainage and excavation. This study is the result of a workshop within the EU COST Action TD1107 (Biochar as option for sustainable resource management), held in Tartu (Estonia) in 2015. The view of stakeholders were consulted on new biochar-based growing media and to what extent peat may be replaced in growing media by new compounds like carbonaceous materials from thermochemical conversion. First positive results from laboratory and greenhouse experiments have been reported with biochar content in growing media ranging up to 50%. Various companies have already started to use biochar as an additive in their growing media formulations. Biochar might play a more important role in replacing peat in growing media, when biochar is available, meets the quality requirements, and their use is economically feasible.
The application of biochar to soil is a potential tool for the long-term sequestration of C and a possible mitigation of greenhouse gas (GHG) emissions. Among the various processes available to produce biochar, hydrothermal carbonization is one technique that is suitable for moist feedstock like digestates from biogas production. The aim of this study was to investigate the stability of C and emissions of NO after the addition of (i) digested wheat ( L.) straw (digestate) and (ii) hydrothermally carbonized (HTC) char of wheat straw as well as (iii) HTC char of digested wheat straw to two soil horizons that differed in C content. The HTC chars were obtained from wheat straw and digested wheat straw that were hydrothermally carbonized at 230°C for 6 h. The digestate and HTC chars were mixed with soil and incubated in 125-mL vessels. The GHG emissions of CO and NO were measured at regular intervals. Additionally, after 108 d, N was applied in the form of NHNO equivalent to 100 kg N ha. After 500 d of incubation, the digestate had lost 34% of C, while the soil mixture with the corresponding HTC char lost 12% of C in the form of CO from the topsoil. The estimated bi-exponential half-life of the recalcitrant C was more than 50% longer for the carbonized material than for the untreated digestate. The NO emissions from both HTC chars were significantly reduced compared with untreated digestate. The reductions were up to 64% for the topsoil and 60% for the subsoil samples. These laboratory results show that HTC holds the potential to increase the C stability of fermented and carbonized biomasses and to reduce NO emissions.
The suitability of iron-ore and blast furnace slag for subsurface flow (SSF) constructed wetlands was studied over a period of four months. Dairy farm wastewater (TP 45 mg l-1) was percolated through buckets planted with reed (volume 9.1 l; hydraulic load 15 l m-2d-1). One group of buckets was kept under aerobic conditions and the other group under anaerobic conditions, monitored by continuous redox potential measurements. Even at high mass loading rates of 0.65 g P m-1d-1 the slag provided 98% removal efficiency and showed no decrease in performance with time. However, phosphorus fractionation data indicate that the high phosphorus retention capacity under aerobic conditions is to a great extent attributable to unstable sorption onto calcium compounds (NH4Cl-P). Phosphorus sorption of both the slag (200 μg P g-1) and the iron-ore (140 μg P g-1) was promoted by predominantly anaerobic conditions due to continuous formation of amorphous ferrous hydroxides. None of the substrates had adverse affects on reed growth.
A short rotation coppice (SRC) with poplar was established in a randomised fertilisation experiment on sandy loam soil in Potsdam (Northeast Germany). The main objective of this study was to assess if negative environmental effects as nitrogen leaching and greenhouse gas emissions are enhanced by mineral nitrogen (N) fertiliser applied to poplar at rates of 0, 50 and 75 kg N ha −1 year −1 and how these effects are influenced by tree age with increasing number of rotation periods and cycles of organic matter decomposition and tree growth after each harvesting event. Between 2008 and 2012, the leaching of nitrate (NO 3 − ) was monitored with self-integrating accumulators over 6-month periods and the emissions of the greenhouse gases (GHG) nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) were determined in closed gas chambers. During the first 4 years of the poplar SRC, most nitrogen was lost through NO 3 − leaching from the main root zone; however, there was no significant relationship to the rate of N fertilisation. On average, 5.8 kg N ha −1 year −1 (13.0 kg CO 2equ ) was leached from the root zone. Nitrogen leaching rates decreased in the course of the 4-year study parallel to an increase of the fine root biomass and the degree of mycorrhization. In contrast to N leaching, the loss of nitrogen by N 2 O emissions from the soil was very low with an average of 0.61 kg N ha −1 year −1 (182 kg CO 2equ ) and were also not affected by N fertilisation over the whole study period. Real CO 2 emissions from the poplar soil were two orders of magnitude higher ranging between 15,122 and 19,091 kg CO 2 ha −1 year −1 and followed the rotation period with enhanced emission rates in the years of harvest. As key-factors for NO 3 − leaching and N 2 O emissions, the time after planting and after harvest and the rotation period have been identified by a mixed effects model.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.