TO-SYN-FUEL Project to Convert Sewage Sludge in Value-Added Products: A Comparative Life Cycle Assessment

The composition of municipal wastewater and sewage sludge reflects the use and proliferation of elements and contaminants within society. In Sweden, official statistics show that concentrations of toxic metals in municipal sewage sludge have steadily decreased, by up to 90 %, since the 1970s, due to environmental programmes and statutory limits on metals in sludge and soil. Results from long-term field experiments show that reduced metal pollution during repeated sewage sludge application has reversed negative trends in soil biology. Despite this Swedish success story, organic waste recycling from Swedish towns and cities to arable land is still limited to only about 20 % of the total amount produced. Resistance among industries and consumers to products grown on land treated with sewage sludge may not always be scientifically grounded; however, there are rational obstacles to application of sewage sludge to land based on its inherent properties rather than its content of pollutants. We argue that application of urban organic wastes to soil is an efficient form of recycling for small municipalities, but that organic waste treatment from large cities requires other solutions. The large volumes of sewage sludge collected in towns and cities are not equitably distributed back to arable land because of the following: (i) The high water and low nutrient content in sewage sludge make long-distance transportation too expensive; and (ii) the low plant availability of nutrients in sewage sludge results in small yield increases even after many years of repeated sludge addition. Therefore, nutrient extraction from urban wastes instead of direct organic waste recycling is a possible way forward. The trend for increased combustion of urban wastes will make ash a key waste type in future. Combustion not only concentrates the nutrients in the ash but also leads to metal enrichment; hence, direct application of the ash to land is most often not possible. However, inorganic fertiliser (e.g. mono-ammonium phosphate fertiliser, MAP) can be produced from metal-contaminated sewage sludge ash in a process whereby the metals are removed. We argue that the view on organic waste recycling needs to be diversified in order to improve the urban–rural nutrient cycle, since only recycling urban organic wastes directly is not a viable option to close the urban–rural nutrient cycle. Recovery and recycling of nutrients from organic wastes are a possible solution. When organic waste recycling is complemented by nutrient extraction, some nutrient loops within society can be closed, enabling more sustainable agricultural production in future.

Recovery of phosphorus from municipal wastewater treatment sludge through bioleaching using Acidithiobacillus thiooxidans

Sewage sludge co-pyrolysis with agricultural/forest residues: A comparative life-cycle assessment

The question of the expediency of increasing the energy efficiency of a large chemical and oil refining industry by using process heat carriers and raw materials as heaters of vapor compression heat pumps based on systems for recuperating heat process losses is considered. A feature of the energy system under consideration is the provision of the main circuit of the heat pump and its drive from a common source of thermal energy. The influence of the temperature parameters of the consumer of highpotential thermal energy, the source of low-potential thermal energy and the energy efficiency of the main functional elements of the energy system under consideration on the ratio of the amount of generated thermal energy supplied to the consumer to the amount of thermal energy losses used is analyzed. In addition, an assessment is made of the influence of the listed factors on the redistribution of low-potential thermal energy flows between the main circuit of the heat pump and its drive. The presented results reflect the fundamental possibility of increasing the temperature level of process heat carriers and raw materials without significant costs for additional external energy sources. The efficiency of reuse of heat losses in a closed technological cycle depends on the temperature conditions of the consumer and the source of thermal energy in the heat pump cycle, on the connection scheme of the thermal energy source and on the energy efficiency of the equipment used.

A review of phosphorus recovery methods at various steps of wastewater treatment and sewage sludge management. The concept of “no solid waste generation” and analytical methods

Phosphorous recovery from sewage sludge via chemical and thermal technologies

Ground source heat pump (GSHP) systems are an extremely efficient space heating and cooling technology. There is a large consensus throughout the literature that GSHP systems can reduce operational CO2 emissions by up to 80% in comparison to natural gas furnace (GF) and air conditioner (AC) systems. The literature is limited; however, in regards to the specific environmental impacts associated with the systems, as well as the impacts that occur throughout the systems’ entire life cycle. In this project, a comparative life cycle assessment was conducted to compare a GSHP system with a GF/AC system, examining 14 specific environmental impact categories. Results were consistent with the literature in regards to the operational stage; however the GSHP system displayed a significantly greater overall environmental impact. While these results are specific to the region of Ontario, Canada, they call into question the prevailing opinion that GSHPs are the more environmentally sustainable option.

Ground source heat pump (GSHP) systems are an extremely efficient space heating and cooling technology. There is a large consensus throughout the literature that GSHP systems can reduce operational CO2 emissions by up to 80% in comparison to natural gas furnace (GF) and air conditioner (AC) systems. The literature is limited; however, in regards to the specific environmental impacts associated with the systems, as well as the impacts that occur throughout the systems’ entire life cycle. In this project, a comparative life cycle assessment was conducted to compare a GSHP system with a GF/AC system, examining 14 specific environmental impact categories. Results were consistent with the literature in regards to the operational stage; however the GSHP system displayed a significantly greater overall environmental impact. While these results are specific to the region of Ontario, Canada, they call into question the prevailing opinion that GSHPs are the more environmentally sustainable option.

Background, Aim and Scope The cow-calf (Bos taurus) industry in subtropical United States and other parts of the world depends almost totally on grazed pastures. Establishment of complete, uniform stand of bahiagrass (BG) in a short time period is important economically. Failure to obtain a good BG stand early means increased encroachment of weeds and the loss of not only the initial investment costs, but production and its cash value. Forage production often requires significant inputs of lime, N fertilizer, and less frequently of P and K fertilizers. Domestic sewage sludge or biosolids, composted urban plant debris, waste lime, phosphogypsum, and dredged materials are examples of materials that can be used for fertilizing and liming pastures. Perennial grass can be a good choice for repeated applications of sewage sludge. Although sewage sludge supply some essential plant nutrients and provide soil property-enhancing organic matter, land-application programs still generate some concerns because of possible health and environmental risks involved. The objectives of this study were to evaluate the cumulative and residual effects of repeated applications of sewage sludge on (i) bahiagrass (BG, Paspalum notatum Flugge) production over years with (1997–2000) and without (2001–2002) sewage sludge applications during a 5-yr period, and (ii) on nutrients status of soil that received annual application of sewage sludge from 1997 to 2000 compared with test values of soils in 2002 (with no sewage sludge application) in South Florida.

Electrodialytic treatment of municipal wastewater and sludge for the removal of heavy metals and recovery of phosphorus

For a sustainable and profitable agriculture production system, balanced and integrated use of nutrients is a key strategy. In addition, partial replacement of chemical fertilizers with organics ones reduces both environmental concerns and economic costs and provides greater soil health benefits. With this hypothesis, an experiment was conducted to assess the yield and economic benefits of a rice-wheat cropping system (RWCS) as influenced by the joint application of sewage sludge (SSL) and fertilizer. The treatments comprised: without fertilizer or SSL; 100% recommended dose of fertilizers (RDF); 100% RDF + 20 Mg ha−1 SSL; 100% RDF + 30 Mg ha−1 SSL; 50% RDF + 20 Mg ha−1 SSL; 60% RDF + 20 Mg ha−1 SSL; 70% RDF + 20 Mg ha−1 SSL; 50% RDF + 30 Mg ha−1 SSL; 60% RDF + 30 Mg ha−1 SSL and 70% RDF + 30 Mg ha−1 SSL. The experiment was laid out in a randomized block design with three replications. The result of our study indicate that the highest percent increase in mean plant height i.e., ~14.85 and ~13.90, and grain yield i.e., ~8.10 and ~18.90 for rice and wheat, respectively, were recorded under 100% RDF + 30 Mg SSL ha−1 treatment compared to 100% RDF, while 70% RDF + 20 Mg ha−1 SSL produced a statistically equivalent grain yield of 100% RDF in RWCS. The application of 20 and 30 Mg SSL ha−1 along with recommended or reduced fertilizer dose, significantly increased the heavy metal content in plant and soil systems above that of 100% RDF, but this enhancement was found within permissible limits. Moreover, the reduced use of SSL i.e., 20 Mg SSL ha−1, resulted in lower heavy metal content in grain and soil than did the 30 Mg ha−1 SSL treatment, but significantly higher than in the absolute control or 100% RDF treatment. In summary, the use of 20 Mg ha−1 SSL along with 70% RDF provided a safer, profitable and sustainable option in a rice-wheat cropping system in the middle Ganegatic alluvial plain.

Sewage sludge drying process integration with a waste-to-energy power plant

Review of sewage sludge management: standards, regulations and analytical methods

Phosphorus recovery from sewage sludge with a hybrid process of low pressure wet oxidation and nanofiltration

Energy recovery and nutrient reuse from sewage sludge has traditionally been achieved via anaerobic digestion/power generation with land application of the biosolids. By contrast, thermal processes such as pyrolysis have typically been used only for energy recovery. One such technology has demonstrated at commercial scale that all of the energy in sludge can be beneficially recovered and reused. No attempt was however made to recover and reuse sludge nutrients. There are many potential benefits of using pyrolysis for both energy and nutrient recovery. Firstly, unlike digestion, the principal energy product is oil, which can readily be stored and used when required, ensuring that energy recovery is maximised. Secondly is that the sludge nutrients are recovered in the pyrolysis char. Laboratory soil incubation studies using char from the Subiaco demonstration plant were conducted over an eight-week period to confirm nutrient availability. Results from this study showed that the phosphorus in the char is plant available although the nitrogen was insoluble. Based on these results it appears that there is potential to use pyrolysis as an effective means to recover and reuse both the energy and the very valuable phosphorus present in sewage sludges.