Leather processing requires substantial inputs of energy, water and chemicals. Additionally, it generates significant amounts of liquid and solid waste, severely impacting the environment. Processing 1 Mg of raw hides yields up to 600–700 kg of waste, considerable amounts of which are solid tannery waste. Such waste contains chromium (Cr) compounds, which are commonly used as tanning agents. This paper reviews solid tannery waste treatment technologies, with emphasis on waste incineration in a specially designed experimental tunnel incinerator. Three different types of tannery waste were subjected to tests: trimmings, shavings and buffing dust. As the research revealed, the process can be applied to all types of solid tannery waste. Moreover, it enables the reuse of the heat of the process and results in a Cr concentrate in the process residues. The conducted analyses (carbon, hydrogen and nitrogen elemental analysis; inductively coupled plasma optical emission spectroscopy; powder X-ray diffraction) proved that there is no or little organic content in the obtained residual ash, which contains up to 53.1%(w/w) Cr in the form of Cr (III) oxide. Such material may be used as a Cr ore substitute in the chemical or metallurgical industries.
Application of additives to waste may influence the course of the biostabilization process and contribute to its higher effectiveness, as well as to a reduction in greenhouse gas and ammonia (NH3) emission from this process. This paper presents research on the impact of biochar addition on the course of the biostabilization process of an undersized fraction from municipal solid waste (UFMSW) in terms of temperature changes, CO2 concentration in the exhaust gases, NH3 emission from the process, as well as changes in the carbon and nitrogen content in the processed waste. Six different biochar additives and three different air-flow rates were investigated for 21 days. It was found that biochar addition contributes to extending the thermophilic phase duration (observed in the case of the addition of 3% and 5% of biochar). The concentration of CO2 in exhaust gases was closely related to the course of temperature changes. The highest concentration of CO2 in the process gases (approx. 18–19%) was recorded for the addition of 10% and 20% of biochar at the lowest air-flow rate applied. It was found that the addition of 3% or a higher amount of biochar reduces nitrogen losses in the processed UFMSW and reduces NH3 emission by over 90% compared to the control.
Understanding perception about nature is paramount to understanding human behavior and decision making on the environment. We performed a survey-based study in Brazil and Poland to better understand the perception of land sparing for nature and the perceived value of nature. The countries were selected by intentional sampling and given their importance for local and global biodiversity conservation, and complex socio-ecological context of conservation versus agroforestry business. We performed an online questionnaire (N = 1030) in Brazil and face-to-face interviews in Poland (N = 322). We found that Brazilian respondents demonstrated more pro-environmental attitudes than Polish survey participants. Regarding the question: “How much nature that is left should be spared?”, nearly 51% of Brazilians answered “everything”, compared with 13% of Polish respondents. Just under half of the respondents from Poland (45.6%) indicated that half of the nature that is left should be spared. Brazilian respondents also perceived the intrinsic value of nature to a greater extent compared with Polish respondents; in total, 76% of Brazilians respondents entirely agreed that “Nature, its plants and animals have a value on their own, independent of their usefulness for us” versus 25% of Polish respondents. Our study contributes to a better understanding of the leverage points driving pro-environmental attitudes in both countries.
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