Economical and environmental implications of solid waste compost applications to agricultural fields in Punjab, Pakistan

Water energy food nexus model: an integrated aqua-agriculture system to produce tilapia and sweet basil using desalinated water

Under the framework of Water-Energy-Food Nexus, this study investigates the integration of solar-powered desalination with aquaculture and agriculture production systems to grow crops. Brackish water desalination is performed using reverse osmosis (RO), the permeate is directed to an aquaculture unit, and the fish effluent is used as irrigation water for crops. The experiment followed a split-plot design with three main variants: a full irrigation schedule for the basil plants with fish effluents as fertilizers, irrigation as fertigation with chemical fertilizers, and a mixed treatment of effluents and chemical fertilizers at 50% application each. Each treatment was further sprayed with or without foliar nutrient application. RO results gave a permeate recovery of 22%, and a salt rejection of 98.7%. In the aquaculture unit, tilapia harvest weight was 0.458 kg with a survival rate of 97.7% and harvest yield of 25 kg/ m3 of water. Effluent treatment exhibited the highest branching and plant height irrespective of the cut number, reaching 17.7 branches and 62-cm height. The effluent treatment under foliar application recorded the highest fresh and dry weights of basil with 14.7 ton/ha and 4.7 ton/ha, respectively. Effluent irrigation plus foliar application recorded basil yield of 5 kg/m3 effluent water. The dominant essential oil elements were linalool (55.5-61.6%), tau.-cadinol (5.3-8.3%), eucalyptol (5.4-7.7%), eugenol (2-6.8%), and (Z,E)-.alpha.-farnesene (3-5.2%). The study is among the very few integrated systems and, in particular, the current study is the first-time investigation of an integrated desalination, aquaculture, and agriculture production using renewable energy. Therefore, results suggest that integrating desalination, aquaculture, and agriculture could be a potential solution for the global water, energy, and food challenges.

Jatropha Curcas Biodiesel: A Lucrative Recipe for Pakistan’s Energy Sector

One of the greatest challenges of the 21st century is to fulfill the growing energy needs sustainably and cost-effectively. Among the different sources of energy, biodiesel is one of the alternative energy sources that has tremendous potential to become a major mainstream renewable energy mix. Jatropha is an important raw input for biodiesel that provides an ecological and sustainable solution for emerging greenhouse gas emissions over the other biomass feedstock. This paper critically evaluates different factors and presents a SWOT analysis (strengths, weaknesses, opportunities, and threats) and barriers to the adoption of Jatropha biodiesel. In Pakistan, the estimated production of Jatropha biodiesel is expected to be 2.93 million tons, that are calculated from available barren land and possible shortlisted suitable areas for Jatropha plantation. It is ~25% of the total import (11.84 million tons) of petroleum products, which can save ~$2 billion USD reserves of Pakistan. The cultivation of Jatropha on barren land is an environmentally and economically lucrative approach for Pakistan. This study has real implications for developing a policy framework related to the environment and socio-economic feasibility of Jatropha biodiesel production in Pakistan.

The impact of agricultural and green waste treatments on compost quality of dewatered sludge

Composting is one of the environmentally desirable methods for the management of sewage sludge. In this process, the organic matters were decomposed by microorganisms. However, different treatments can improve their qualities. This study aimed to investigate the effect of two agricultural waste wheat straw (WS) and green waste eucalyptus tree leaves (ETL) treatments on the quality of the compost produced from dewatered sewage sludge. So that, the variation trend of heavy metals, temperature, moisture, PH, and C/N ratio was considered during the composting process. The results showed that the variation of some parameters in WS and ETL such as temperature (24.68 ± 0.26 and 23.41 ± 1.35), moisture (4.5 ± 2.64 and 7.66 ± 2.51), pH (5.66 ± 0.35 and 5.97 ± 0.41), and C/N ratio (250 ± 4.08 and 60 ± 3.21) was suitable in both windrows, respectively. Likewise, trend of mineralization was suitable in both masses, because TVS (43 to 78 mg/g DW for WS and 45 to 69 mg/g DW for ETL) and TDS (21 to 55 mg/g DW for WS and 2.6 to 38 mg/g DW for ETL) decreased and increased, respectively, in the composting process. While fecal coliform (2.72 MPN/g DW) and EC (2.4mmho/cm) at WS was more than Iran's agricultural standard. As a consequence, although the quality of both masses was suitable and similar, there are some limitations for using treated compost by WS in agricultural lands due to higher levels of EC, fecal coliforms, and manganese. Therefore, quality of dewatered sludge treated compared with ETL is higher than WS. Furthermore, improvement process and application of some pretreatments are necessary for decreasing the heavy metals.

Valorisation of fish by-products against waste management treatments--Comparison of environmental impacts

Reuse and valorisation of fish by-products is a key process for marine resources conservation. Usually, fishmeal and oil processing factories collect the by-products generated by fishing port and industry processing activities, producing an economical benefit to both parts. In the same way, different added-value products can be recovered by the valorisation industries whereas fishing companies save the costs associated with the management of those wastes. However, it is important to estimate the advantages of valorisation processes not only in terms of economic income, but also considering the environmental impacts. This would help to know if the valorisation of a residue provokes higher impact than other waste management options, which means that its advantages are probably not enough for guarantying a sustainable waste reuse. To that purpose, there are several methodologies to evaluate the environmental impacts of processes, including those of waste management, providing different indicators which give information on relevant environmental aspects. In the current study, a comparative environmental assessment between a valorisation process (fishmeal and oil production) and different waste management scenarios (composting, incineration and landfilling) was developed. This comparison is a necessary step for the development and industrial implementation of these processes as the best alternative treatment for fish by-products. The obtained results showed that both valorisation process and waste management treatments presented similar impacts. However, a significant benefit can be achieved through valorisation of fish by-products. Additionally, the implications of the possible presence of pollutants were discussed.

Use of municipal solid waste compost as a growth media for an energy plant (rapeseed)

Objective of this work was to study the effect of mixtures of municipal solid waste (MSW) compost with a peat based growth media on the yields of rapeseed. The MSW compost and the peat were respectively mixed at ratios equal to 10%:90%, 20%:80% and 50%:50% (wet weight basis). A randomized block design was adopted with 5 treatments and 3 blocks per treatment. The 50%:50% mixture achieved a statistically higher yield (dry weight and average leaf area) compared to all other treatments, whilst compost alone led to the lowest shoot growth. Negative correlations were calculated between the total contents of Pb, Ni and Cd of the plant tissues and the corresponding dry weights of the shoots. Regression equations were developed that described shoot yields as a function of the water holding capacity, pH, electrical conductivity, C/N ratio and the total and leachable contents of certain metals in the growth media.

Accumulation and spatial distribution of Cd, Cr, and Pb in mulberry from municipal solid waste compost following application of EDTA and (NH4)2SO4

Municipal solid waste compost can be used to cropland as soil amendment to supply nutrients and improve soil physical properties. But long-term application of municipal solid waste (MSW) compost may result in accumulation of toxic metals in amended soil. Phytoremediation, especially phytoextraction, is a novel, cost-effective, and environmentally friendly approach that uses metal-accumulating plants to concentrate and remove metals from contaminated soils. Ethylenediaminetetraacetate (EDTA) was applied to metal-contaminated soil to increase the mobility and phytoavailability of metals in soil, thereby increasing the amount of toxic metals accumulated in the upper parts of phytoextracting plants. The objectives of this study were (1) to investigate the accumulation and spatial distribution of toxic metals (Cd, Cr, and Pb) in mulberry from MSW compost with the application of EDTA and (NH(4))(2)SO(4), (2) to examine the effectiveness of EDTA and (NH(4))(2)SO(4) applied together on toxic metals (Cd, Cr, and Pb) removal by mulberry under field conditions, and (3) to evaluate the potential of mulberry for phytoextraction of toxic metals from MSW compost. The tested plant-mulberry had been grown in MSW compost field for 4 years. EDTA solution at five rates (0, 50, 100, 50 mmol L(-1) + 1 g L(-1) (NH(4))(2)SO(4), and 100 mmol L(-1) + 1 g L(-1) (NH(4))(2)SO(4)) was added into mulberry root medium in September 2009. Twenty days later, the plants were harvested and separated into six parts according to plant height. Cd, Cr, and Pb contents in plant samples and MSW compost were analyzed using an atomic absorption spectrophotometer. In the same treatment, Cd, Cr, and Pb concentrations in mulberry shoot were all higher than those in root, and Cd and Pb concentrations in shoot increased from lower to upper parts, reaching the highest in leaves. Significant increases were found in toxic metal concentration in different parts of mulberry with increasing EDTA concentration, especially when combined with (NH(4))(2)SO(4). Mulberry exhibited high ability to accumulate Cd with bioconcentration factors (BCFs) higher than 1. EDTA application also significantly increased Cd BCFs. More than 30 % of metal uptake was concentrated in mulberry branches (stem of above 100 cm height) and leaves. Results presented here show that mulberry is a woody plant that has the potential of Cd phytoextraction from MSW compost by removing leaves and cutting branches. The application of EDTA combined with (NH(4))(2)SO(4) significantly enhanced the efficiency of mulberry in removing Cd from the compost medium. Adding (NH(4))(2)SO(4) into the compost will lower the risk of the exposure of environment to excessive non-biodegradable EDTA in a large-scale EDTA-assisted phytoextraction by reducing the dosage of EDTA. In China, the need for sod is increasing day by day. Sod is often produced on arable soil and sold together with soils. This would lead to the soil being infertile and the soil layer thin. After several times' production, the soil can no longer be used for cultivating crops and be destroyed. In order to fully utilize MSW compost resources and save valuable soil resources, MSW compost can be used to replace arable soil to produce sod after extraction of toxic metals in it.

The effects of recycling loops in food waste management in Japan: based on the environmental and economic evaluation of food recycling

In Japan, a revised Food Recycling Law went into effect in 2007 to promote a "recycling loop" that requires food industries to purchase farm products that are grown using food waste-derived compost/animal feed. To realize and expand food recycling, it is necessary to evaluate how the recycling facilities work in the recycling loop. The purpose of this study is to assess the environmental and economic efficiency of the food recycling facilities that are involved in the recycling loop, which are also known as looped facilities. The global warming potential and running cost of five looped facilities were evaluated by LCA (life cycle assessment) and LCC (life cycle cost) approaches: machine integrated compost, windrow compost, liquid feed, dry feed, and bio-gasification. The LCA results showed low total GHG (greenhouse gas) emissions of -126 and -49 kg-CO(2)/t-waste, respectively, for dry feed and bio-gasification facilities, due to a high substitution effect. The LCC study showed a low running cost for composting facilities of -15,648 and -18,955 yen/t-waste, respectively, due to high revenue from the food waste collection. It was found that the mandatory reporting of food waste emitters to the government increased collection fees; however, the collection fee in animal feed facilities was relatively low because food waste was collected at a low price or nutritious food waste was purchased to produce quality feed. In the characterisation survey of various treatment methods, the composting facilities showed a relatively low environmental impact and a high economic efficiency. Animal feed facilities had a wide distribution of the total GHG emissions, depending on both the energy usage during the drying process and the substitution effect, which were related to the water content of the food waste and the number of recycled products. In comparison with incineration, the majority of the food recycling facilities showed low GHG emissions and economic effectiveness. This paper also reported on the effects of recycling loops by comparing looped and non-looped animal feed facilities, and confirmed that the looped facilities were economically effective, due to an increased amount of food waste collection.

Inventory of heavy metal content in organic waste applied as fertilizer in agriculture: evaluating the risk of transfer into the food chain

BACKGROUND, AIM, AND SCOPE

In this work, an environmental risk assessment of reusing organic waste of differing origins and raw materials as agricultural fertilizers was carried out. An inventory of the heavy metal content in different organic wastes (i.e., compost, sludge, or manure) from more than 80 studies at different locations worldwide is presented.

MATERIALS AND METHODS

The risk analysis was developed by considering the heavy metal (primarily Cd, Cu, Ni, Pb, and Zn) concentrations in different organic residues to assess their potential environmental accumulation and biotransfer to the food chain and humans. A multi-compartment model was used to estimate the fate and distribution of metals in different environmental compartments, and a multi-pathway model was used to predict human exposure.

RESULTS

The obtained hazard index for each waste was concerning in many cases, especially in the sludge samples that yielded an average value of 0.64. Among the metals, Zn was the main contributor to total risk in all organic wastes due to its high concentration in the residues and high biotransfer potential. Other more toxic metals, like Cd or Pb, represented a negligible contribution.

CONCLUSIONS

These results suggest that the Zn content in organic waste should be reduced or more heavily regulated to guarantee the safe management and reuse of waste residues according to the current policies promoted by the European Union.

A risk-based decision tool for the management of organic waste in agriculture and farming activities (FARMERS)

Currently, specific management guidelines must be implemented for guaranteeing the safe reuse of organic waste in agriculture. With that aim, this work was focused on the development of a decision support tool for a safe and sustainable management of cattle manure as fertiliser in pastureland, to control and limit metal accumulation in soil and to reduce metal biotransfer from soil to other compartments. The system was developed on the basis of an environmental risk assessment multi-compartmental model. In contrast to other management tools, a long-term dynamic modelling approach was selected considering the persistence of metals in the environment. A detailed description of the underlying flow equations which accounts for distribution, human exposure and risk characterisation of metals in the assessed scenario was presented, as well as model parameterization. The tool was implemented in Visual C++ and is structured on a data base, where all required data is stored, the risk assessment model and a GIS module for the visualization of the scenario characteristics and the results obtained (risk indexes). The decision support system allows choosing among three estimation options, depending on the needs of the user, which provide information to both farmers and policy makers. The first option is useful for evaluating the adequacy of the current management practices of the different farms, and the remaining ones provides information on the measures that can be taken to carry out a fertilising plan without exceeding risk to human health. Among other results, maximum values of application rates of manure, maximum permissible metal content of manure and maximum application times in a particular scenario can be estimated by this system. To illustrate tool application, a real case study with data corresponding to different farms of a milk production cooperative was presented.