Feasibility of cross-laminated secondary timber

The construction industry creates significant volumes of waste timber, much of which has residual quality and value that dissipates in conventional waste management. This research explored the novel concept of reusing secondary timber as feedstock for ‘cross-laminated secondary timber’ (CLST) through a review of the literature. If CLST can replace conventional cross-laminated timber (CLT), structural steel and reinforced concrete in some applications, this constitutes upcycling to displace materials with greater environmental impacts. The paper introduces the rationale for such an intervention and assesses its feasibility. It concludes with open research questions to advance the concept towards commercial application

Recognising waste use potential to achieve a circular economy

Waste management historically focused on the protection of human health and the natural environment from the impacts of littering and dispersion of pollutants. An additional and more recent concern is the resource value of waste. Our analysis shows that the regulatory concept of waste in the European Union, which comprises environmental principles, the legal definition of waste, legal requirements, and policy implementation, is not fit for addressing this concern. The legal definition of waste overlooks the context of waste, fails to consider the interests of the waste user as opposed to the waste holder, and aims to control the impacts of careless discarding rather than stimulating careful discarding. To address these challenges, we suggest a legal requirement to recognise the potential of waste to be used, operationalised by formulating a waste use potential, which expresses how and how much waste can be used as a resource, given enabling conditions. Recognition of waste use potential highlights local opportunities for reuse and recovery, reduces the likelihood of careless discarding, and reveals the interests of possible waste users to the waste holder. The waste use potential may be employed in the formulation and evaluation of policies for industrial and municipal solid waste in a circular economy

Life Cycle Assessment Model for Biomass Fuel Briquetting

Purpose: Previous Life Cycle Assessment (LCA) studies of biomass briquetting have shown wide variations in the LCA outcomes as a result of variations in LCA methodological parameters and briquetting technological parameters. An LCA model of biomass briquetting was therefore developed to enable transparent comparison of life cycle environmental impacts of briquetting with individual or blends of biomass feeds with a variety of technological options. // Methods: The model was developed according to the standard LCA procedure of ISO14044. A comparative approach was utilised, and a set of integrated excel worksheets that describe process flows of material, energy and emissions across different units of the briquetting process was used in developing the model components. // Results: The main model components include materials and process inventory databases derived from standard sources, main process calculations, user inputs and results sections. The model is open-access in a user accessible format (Microsoft Excel). A representative case study with mixed rice husks and corn cobs was used in validating the model. Results showed that the briquetting unit made the largest contribution, 42%, to the total life cycle operational energy of the briquetting system. For all the blends of rice husks and corn cobs explored in this study, the total life cycle energy of briquetting was in the range 0.2 to 0.3 MJ/MJ. For the same blend ratios, a total life cycle energy of briquetting in the range 0.2 to 1.7 MJ/MJ was also obtained with change in other LCA input parameters, in a sensitivity test. An increase in rice husk content of the blend increased the environmental impact of briquetting in terms of global warming potential (kg CO2-eq), acidification potential (kg SO2-eq), human toxicity (kg 1,4-DB-eq), ozone layer depletion (kg CFC-11-eq), and terrestrial ecotoxicity (kg 1,4-DB-eq) per MJ briquette energy content, as it was associated with a lower briquette density, which increased the energy required for handling

The potential role of energy-from-waste air pollution control residues in the industrial ecology of cement

Industrial ecology draws an analogy between industrial activity and natural ecosystems with the inherent implication that, in its ideal form, an industrial ecosystem cycles resources efficiently, with minimization of waste. Industrial symbiosis between the cement and other industries can make a substantial contribution to sustainability. About 3.6 Gt of cement was produced globally in 2011, consuming more than 5 Gt of raw materials and about 11% of total industrial energy, and leading to about 7% of global CO2 emissions. In the same year, global generation of municipal solid waste was estimated at 1.3 Gt, of which about 16% was thermally processed, usually by combustion to generate energy-from-waste (EfW). This equates to about 2.1% of total industrial energy consumption, but would generate about 6 Mtpa of air pollution control (APC) residues. Use of these EfW APC residues in blended cements has been suggested, but they contain soluble toxic elements and are classified as hazardous wastes in most jurisdictions. This paper discusses the effects of incorporating EfW APC residues on the technical performance of blended cements, and on several characteristics of importance for the environmental acceptability of this practice, including (1) total inorganic pollutant concentrations in blended cements, (2) pH-dependent leachability of toxic metal pollutants, e.g. according to BS EN 12457-2, and DD CEN/TS 15364, and (3) diffusion-controlled leaching of monolithic blended cement pastes, e.g. according to EA NEN 7375. Potential pollutants, especially Pb and Zn, but also Cd, Hg, Sb, Sn, and Se, were found to be enriched in EfW APC residues relative to cements. Apart from their potential to pollute the environment, metals in APC residues can affect cement hydration and hardening, and this has been observed. EfW APC residues also contain high levels of several elements that are problematic for quality control of blended cements, notably chloride, which causes steel reinforcement corrosion, and alkalis (Na and K) implicated in the destructive alkali–silica reaction. Although leaching data for both granular and monolithic samples suggest that the mobility of low concentrations of metal pollutants is reduced in cement-based matrices, leachability of chloride remains high and leaching of soluble constituents in APC residues can also be expected to increase paste porosity over time. Furthermore, the literature indicates that pozzolanic or cementing properties of EfW APC residues are not sufficiently strong or reliable to justify their use as a cement replacement, and there is also the potential for components of APC residues to cause other deleterious expansion reactions in cement-based materials. Therefore, industrial ecology cannot solve the problem of management of EfW APC residues through incorporating them in blended cements without radically re-thinking the principle that ‘dilution is not the solution to pollution,’ which underlies much waste management policy and legislation. Relaxation of these principles would also have undesirable implications for numerous other hazardous wastes. Management of such wastes by blending into cements might seem convenient, but could ultimately lead to wide uncontrolled dispersal of pollutants, especially in cement product recycling, and undermine the quality of blended cements. Originality: This paper considers the technical benefits and environmental acceptability of using EfW APC residues in blended cement production, with a focus on the fate and behavior of the toxic metal concentrations in the APC residues. It summarizes the available information on this subject, and provides a critical analysis and discussion aimed at the cement and waste management industries, as well as policy-makers, to assist in decision-making

Comparison of environmental impacts of individual meals - Does it really make a difference to choose plant-based meals instead of meat-based ones?

More than one third of global greenhouse gas emissions (GHG) can be attributed to our food system. Limiting global warming to 1.5° or 2 °C will not be possible without reducing GHG emissions from the food system. Dietary change at the meal level is of great importance as day-to-day consumption patterns drive the global food production system. The aim of this paper was to assess the life cycle environmental impact of a sample of meals from different cuisines (chilli, lasagne, curry and teriyaki meals) and their meat-based, vegetarian, vegan, and whole-food vegan recipe variations. The environmental impacts (global warming, freshwater eutrophication, terrestrial acidification and water depletion potential) of 13 meals, made with 33 different ingredients, were estimated from cradle to plate using Life Cycle Assessment (LCA). Results showed that irrespective of the type of cuisine, the plant-based version of meals (vegan and whole-food vegan) had substantially lower environmental impacts across all impact categories than their vegetarian and meat-based versions. On average, meat-based meals had 14 times higher environmental impact, while vegetarian meals had 3 times higher environmental impact than vegan meals. Substantial reductions in the environmental impacts of meals can be achieved when animal-based ingredients (e.g., beef, cheese, pork, chicken) are replaced with whole or minimally processed plant-based ingredients (i.e., vegetables, legumes) in recipes. Swapping animal-based meals for plant-based versions, and preferably transitioning to plant-based diets, present important opportunities for mitigating climate change and safeguarding environmental sustainability

Effects of operating variables on durability of fuel briquettes from rice husks and corn cobs

Biomass densification processes increase fuel energy density for more efficient transport. This study presents new data to show that blending different types of biomass improves the properties of densified biomass briquettes. The specific objectives were to investigate the effects of sample batch (biomass source), material ratio (rice husks to corn cobs), addition of binder (starch and water mixture) and compaction pressure, on briquette properties, using a factorial experiment. Briquettes had a unit density of up to 1.9 times the loose biomass bulk density, and were stronger than briquettes from the individual materials. Considering average values from two biomass sources, an unconfined compressive strength of 176 kPa was achieved at a compaction pressure of 31 MPa for a 3:7 blend of rice husks to corn cobs with 10% binder. These briquettes were durable, with only 4% mass loss during abrasion and 10% mass loss during shattering tests. They absorbed 36% less water than loose corn cobs. Statistical analysis of the results showed that starch and water addition was required for adequate briquette strength, but significantly reduced green and relaxed densities. The source of the biomass had a significant effect on densification, which emphasises the need to understand factors underlying biomass variability

Biosolids and microalgae as alternative binders for biomass fuel briquetting

Binders can be employed to improve the particle adhesion, compressive strength, abrasion resistance and energy content of densified biomass, such as briquettes. They may also reduce the energy cost of producing such briquettes, by reducing the compaction pressure, conditioning temperature and the wear on production equipment. This study explored and compared the effects of three different binders, including starch, enhanced treated biosolids and microalgae, on density, durability, energy content and combustion characteristics of fuel briquettes produced from blends of rice husks, corn cobs and bagasse, in a multilevel factorial design experiment. Briquettes had relaxed unit densities of 1.9–3.3 times the loose biomass bulk density, and were stronger than briquettes from the individual materials, with an average unconfined compressive strength of 125 kPa. An unconfined compressive strength of 175 kPa was achieved for a 2:4:1 blend of rice husks, corn cobs and bagasse with the microalgae binder at a compaction pressure of 31 MPa. Statistical analysis of the results showed that the addition of biosolids and microalgae binders significantly improved briquette density, while the addition of starch reduced briquette density, and biosolids reduced briquette strength. Of all the briquettes produced with the three binders, those containing the microalgae binder were found to be most durable, with a higher energy value, slower mass loss during briquette combustion, and a higher afterglow time. Since microalgae may be grown using CO2 from biomass combustion, discovery of their advantages as a binder in briquetting is particularly welcome

Characterising existing buildings as material banks (E-BAMB) to enable component reuse

As-built records for existing buildings tend to be poor. Components that make up the existing building stock must be better characterised to prevent them becoming waste. The first record of materials in an existing building is often the waste report, which classifies materials for waste management and gathers information after the opportunity for higher-value reuse of components has passed. Policy at various levels aims to increase reuse, but an understanding of ‘existing buildings as material banks’ (E-BAMB) is a necessary precursor to overcoming other barriers. This paper reviews the current means of understanding E-BAMB and identifies its shortfalls. This analysis leads to the conception of a strategy in which the various approaches are organised as an information system. The future role of technology and mandatory provision of E-BAMB information at the planning stage are explored. The proposed system would enable specifiers, manufacturers and academics to assess the wealth of materials that can be reused, repurposed or upcycled in new projects or businesses. This does not guarantee that actual reuse will occur, as financial, technical and legal barriers may remain. However, it creates the context for assessing secondary components against their virgin equivalents and the enabling conditions for new circular business models

Nickel speciation in cement-stabilized/solidified metal treatment filtercakes

Cement-based stabilization/solidification (S/S) is used to decrease environmental leaching of contaminants from industrial wastes. In this study, two industrial metal treatment filtercakes were characterized by X-ray diffractometry (XRD), thermogravimetric and differential thermogravimetric analysis (TG/DTG) and Fourier transform infrared (FTIR); speciation of nickel was examined by X-ray absorption (XAS) spectroscopy. Although the degree of carbonation and crystallinity of the two untreated filtercakes differed, α-nickel hydroxide was identified as the primary nickel-containing phase by XRD and nickel K edge XAS. XAS showed that the speciation of nickel in the filtercake was unaltered by treatment with any of five different S/S binder systems. Nickel leaching from the untreated filtercakes and all their stabilized/solidified products, as a function of pH in the acid neutralization capacity test, was essentially complete below pH ∼5, but was 3–4 orders of magnitude lower at pH 8–12. S/S does not respeciate nickel from metal treatment filtercakes and any reduction of nickel leaching by S/S is attributable to pH control and physical mechanisms only. pH-dependent leaching of Cr, Cu and Ni is similar for the wastes and s/s products, except that availability of Cr, Cu and Zn at decreased pH is reduced in matrices containing ground granulated blast furnace slag