The study combined rainwater harvesting (RWH), agroforestry (AFS) and soil organic amendment in a holistic approach with the aim to address water scarcity and enhance crop yield in dry areas with limited moisture and depleted soil. The field experiment was conducted in eastern Tigray- Ethiopia following detailed RWH site suitability assessment and evaluation of existing RWH and AFS systems. The results showed BWAFS (RWH, poultry biochar and AFS) significantly increased pH, SOM, TN, Av.P as well as yield and biomass of both crops (maize and barley). The study proved the potential of the holistic approach for improving soil quality and crop yield in arid and semi-arid regions facing water scarcity

The study combined rainwater harvesting (RWH), agroforestry (AFS) and soil organic amendment in a holistic approach with the aim to address water scarcity and enhance crop yield in dry areas with limited moisture and depleted soil. The field experiment was conducted in eastern Tigray- Ethiopia following detailed RWH site suitability assessment and evaluation of existing RWH and AFS systems. The results showed BWAFS (RWH, poultry biochar and AFS) significantly increased pH and SOM, TN and Av.P as well as yield and biomass of both crops (maize and barley). The study proved the potential of the holistic approach for improving soil quality and crop yield in arid and semi-arid regions facing water scarcity.

The sustainable availability and resilient supply of safe drinking water remains a challenge that is far from fulfilled. As of 2024, around 2 billion people worldwide do not have access to safe drinking water. The regions of Sub-Saharan Africa and South Asia are the most vulnerable regions in this regard. This is despite the fact that these regions are home to some of the world’s fastest-growing economies. However, economic growth and rapid urbanization may also be connected to the increasing water stress in the suburban and rural areas. We propose addressing the two main challenges in this regard, which are the selection of the suitable treatment and distribution systems for different contexts using a decision support system following a Whole-of-Resource Approach (WORA). This approach considers the different water sources and sinks as contributing to a positive or negative change in the single resource, irrespective of whether the resource, in this case water, is used for domestic, industrial, or agricultural purposes. In this regard, this paper presents an illustrative proof of concept for such a decision support tool based on a multiple-criteria decision analysis. The decision support tool is aimed at facilitating water management within a WORA by providing recommendations regarding rainwater harvesting and savings in agricultural water consumption, in addition to suggesting water treatment and distribution systems, enabling systemic water resource management adapted to local context-specific conditions and needs.

With the growing awareness of microplastics in the environment, the question of microplastics as remnants of biodegradable plastic (BDP) products is gaining momentum. BDP bags for kitchen waste collection are often certified as fully compostable as proof of industrial compostability. Frequently certification is done using under standardized laboratory conditions within 12 weeks. Composting plants often process biowaste into compost in a shorter time under inhomogeneous conditions. This study investigates the decomposition behavior of commercially available BDP bags for kitchen waste collection at an industrial composting plant within a practically realistic time frame of 6 weeks. The research determines the decomposition behavior under practice conditions. Four bag types, two made from thermoplastic starch (TPS) blends and two from polylactic acid (PLA) blends underwent composting. The decomposition was evaluated by examining the remaining macro- (> 8 mm), meso- (2–8 mm), and microparticles (1–2 mm) in the compost with different methods. After 6 weeks, the mass-based decomposition rate of TPS blend bags exceeded 95%. In contrast, PLA blend bags failed to reach a decomposition rate of 90%. The study did not depict very small particles <1 mm. However, they are present. The study findings indicate that composting time and conditions, inhomogeneities, as well as the bag type are crucial factors influencing the decomposition of BDP bags. Concerns are raised about the usefulness of DIN 13432 as certification scheme for industrial conditions.

In diesem Bericht stellt die Hamburg Open Online University an der TU Hamburg (HOOU@TUHH) ihre Arbeit im Jahr 2023 vor.

Micropollutants are present in low concentration in water bodies. Due to an inadequate elimination in municipal, mechanical-biological wastewater treatment plants, they represent a main path of entry. In addition to the establishment of micropollutant elimination, e.g. as a fourth treatment step, increasing the energy efficiency of wastewater treatment plants is a current issue in urban water management. The alternative wastewater treatment plant concept MicroStop addresses both issues. In addition to an all-encompassing reduction of particles, nutrients, and multiresistant germs, micropollutants are eliminated by a combination of biological degradation in fixed-bed reactors with physical retention by nanofiltration. The combination process is preceded by enhanced carbon extraction in the pre-treatment stage by coagulation/flocculation. To assess the feasibility of the concept, tests were carried out for enhanced carbon extraction and the biological degradation of micropollutants under nitrification and denitrification in the fixed-bed reactors. Using the coagulation/flocculation chemical Sachtofloc 46.12 at a dosage of 0.2 mmol Al/L wastewater, a further reduction in total organic carbon (TOCN) in the primary clarification effluent of 49 % (wastewater treatment plant A) and 30 % (wastewater treatment plant B) was achieved in 1 Liter jar tests. The reduction was limited by the proportion of dissolved organic carbon (DOCN) in the wastewater, which was 52 % (wastewater treatment plant A) and 68 % (wastewater treatment plant B). A combination of the MicroStop concept with other processes for enhanced carbon extraction, such as POWERSTEP, is possible based on the overall results. In the biological fixed-bed reactors, nitrification with > 99 % reduction and denitrification with 94 – 99 % could be established. In one test phase, nitrite accumulation occurred, which was prevented by adjusting the acetic acid dosage. Three test phases (purely aerobic operation and nitrification/denitrification without/with flocculation supernatant) demonstrated further potential for the biodegradation of some of the pollutants tested. For gabapentin (> 93 to > 98 %), iomeprol (> 69 to > 96 %) and metoprolol (> 62 to > 76 %), very good elimination rates below the limit of quantification were achieved in all test phases under aerobic conditions (with/without nitrification). Diclofenac was reduced with 47 to 67 %, better than known from literature, but never below a threshold concentration of 1.8 – 2.6 µg/L. A longer retention time showed a positive influence. Sulfamethoxazole showed fluctuating results with degrees of elimination between – 42 and 87 %. A reduction only occurred under denitrification and became more stable under increased acetic acid dosing during a longer retention time. Under aerobic conditions, there was an increase in pollutants. A retransformation of the main metabolite N4-acetylsulfamethoxazole is assumed to be the cause. Carbamazepine and its metabolite carbamazepine 10,11-epoxide showed persistent behaviour. The sweetener cyclamate was only detected in one test phase and was very well eliminated with 97 %.

Food security and energy transition are among the current major global environmental challenges. Although these issues individually are significant in their own right, they are connected to each other in a nexus with different interrelationships and dependencies. In the quest for non-fossil alternatives for energy, cultivation of bioenergy crops has become an important part of the energy policy in many countries. In this regard, the use of fertile agricultural land for growing crops for energy production rather than for food supply affects the global food security. Recent conflicts and the geopolitical crisis in Europe, leading to increased food, fuel, and fertiliser prices, the existing climate crisis, and the crisis caused due to the COVID-19 pandemic, have further reinforced the understanding of this nexus, with certain countries mulling limiting biofuel production from agricultural land and others banning food grain exports to safeguard food supply. The idea of growing non-food energy crops on marginal lands in general and closed landfill sites in particular is hence ever more relevant, to avoid land-use concurrence between food needs and energy needs. Landfilling has been the dominant waste management strategy until recently in European countries and is still the dominant mode of waste management in low-income regions like South Asia. This paper provides a review of the economic as well as environmental benefits of growing Ricinus communis L., Jatropha curcas L., and Populus deltoides as energy crops on closed landfill sites in the South Asian context. While as the cultivation of Miscanthus X Giganteus, Silphium perfoliatum L., and Panicum virgatum (Switchgrass) is reviewed in the European context. The cultivation of non-food energy crops like these on closed landfill sites and marginal lands is presented as a potential component of an integrated food-energy policy, with an increased relevance in the current times. In the current times of multiple crises, this measure is of increasing relevance as a part of the overall strategy to achieve resilience and environmental sustainability.

Deinking sludges are residues generated from deinking operation during wastepaper recycling. The common treatment option in Europe includes dewatering steps followed by incineration. Incineration of deinking sludge is capital intensive and not sustainable hence it was investigated if it can be valorized energetically by anaerobic digestion and materially by calcium carbonate recovery. Investigations were carried out by characterisation of substrates and execution of experiments. The dry matter of deinking sludges depends on the dewatering stage in treatment plant and is in the range of 2 to 40% fresh mass. The pre-dewatered deinking sludge has a dry matter content of 5 - 16% fresh mass. The organic dry matter of deinking sludges is in the range of 29 to 33% DM. Calcium carbonate and ash contents have the highest fraction of dry matter in deinking sludges and are 47 - 52% DM and 67 - 71% DM respectively. Deinking sludges showed good digestibility with common inocula and their biogas yield was observed to be about half of that of cellulose under similar anaerobic conditions. Pre-dewatered deinking sludge from the mixture of high and medium wastepaper grades showed the highest specific biogas yield (417 ± 0 NL/kg·oDM) followed by those with a mixture of medium wastepaper grades (275 ± 14 NL /kg·oDM) and lastly those from ordinary wastepaper grades (250 ± 21 NL /kg·oDM). A carbon to nitrogen ratio in the range of 29 and 34 is recommended to improve the efficiency of a semi-continuously operated anaerobic digestion of deinking sludge. Within the scope of this study, a hydraulic retention time of 19 days which corresponds to an organic loading rate of 1.6 ± 0.42 kg oDM/m3·d was observed as optimal for anaerobic digestion of deinking sludge using a semi-continuous system. Deinking sludge settles quickly in bioreactors, hence an efficient mixing mechanism during semi-continuous process is recommended. The two-step first order kinetics showed the best fitting for the anaerobic digestion of raw and pre-dewatered deinking sludges from ordinary wastepaper grades. The modified Gompertz model showed the best fit for pre-dewatered deinking sludges from high and medium wastepaper grades. The ashes of deinking sludges and its digestates are rich in calcium carbonate and contain some elements found in portland cement but in different proportion. The ashes contribute to flexural and compressive strength which make them suitable as supplementary building materials. Results obtained from the study show that biogas production from deinking sludges combined with calcium carbonate recovery is a sustainable approach.