Mineralisation of CO2 in wood biomass ash for cement substitution in construction products

This study extends our exploration of the potential of biomass ashes for their CO2-reactivity and self-cementing properties. The ability of three hardwood-based biomass ashes to mineralise CO2 gas and partially replace CEM I in mortars was investigated. The three hardwoods were English oak (Quercus rober), English lime (Tilia x europaea), and beech (Fagus sylvatica). The woody biomass wastes were incinerated at 800°C to extract their key mineral phases, which are known to be reactive to CO2 gas to form carbonates. The selected biomass ashes were analysed for their CO2-reactivity, which was in the range of 32–43% (w/w). The ashes were used to replace CEM I at 7 and 15% w/w and this “binder” was mixed with sand and water to produce cylindrical monolithic samples. These monoliths were then carbonated and sealed cured over 28 days. The compressive strength, density and microstructure of the carbonate-hardened monoliths were examined. The ash-containing monoliths displayed mature strengths comparable to the cement-only reference samples. The CO2 uptake of oak containing monoliths was 7.37 and 8.29% w/w, for 7 and 15% ash substitutions, respectively. For beech and English lime they were 4.96 and 6.22% w/w and 6.43 and 7.15% w/w, respectively. The 28 day unconfined compressive strengths for the oak and beech ashes were within the range of ~80–94% of the control, whereas lime ash was 107% of the latter. A microstructural examination showed carbonate cemented sand grains together highlighting that biomass ash-derived minerals can be very CO2 reactive and have potential to be used as a binder to produce carbonated construction materials. The use of biomass to energy ash-derived minerals as a cement replacement may have significant potential benefits, including direct and indirect CO2 emission savings in addition to the avoidance of landfilling of these combustion residues

Construction: use waste for building

As construction work in India soars and the pressure on stone and other natural resources mounts, the Bureau of Indian Standards has called for good-quality building materials to be made from waste products. A proof of concept for this waste valorization has been developed by the Indo-UK Centre for Environment Research and Innovation (IU-CERI; see www.gre.ac.uk/iu-ceri). IU-CERI has identified agricultural and industrial wastes from India that can be converted into value-added products such as construction materials by using carbon dioxide and commercial low-carbon technology (P. J. Gunning et al. Proc. Inst. Civil Eng. Construct. Mater. 164, 231–239; 2011). These products meet European specifications for lightweight aggregates. Implementing this technology will help to utilize India's abundant wastes from agriculture (more than 800 million tonnes), mining and industry (more than 400 million tonnes). These sectors will benefit from economic gains and smaller carbon footprints. Other likely benefits include diversion of waste from burning or landfill, sustainable production of construction materials, and more-consistent supply chains in regions with sparse natural resources

Biomass waste utilisation in low-carbon products: harnessing a major potential resource

The increasing demand for food and other basic resources from a growing population has resulted in the intensification of agricultural and industrial activities. The wastes generated from agriculture are a burgeoning problem, as their disposal, utilisation and management practices are not efficient or universally applied. Particularly in developing countries, most biomass residues are left in the field to decompose or are burned in the open, resulting in significant environmental impacts. Similarly, with rapid global urbanisation and the rising demand for construction products, alternative sustainable energy sources and raw materials supplies are required. Biomass wastes are an under-utilised source of material (for both energy and materials generation) and to date there has been little activity focussing on a ‘low-carbon’ route for their valorisation. Thus, the present paper attempts to address this by reviewing the global availability of biomass wastes and their potential for use as a feedstock for the manufacture of high-volume construction materials. Although targeted at practitioners in the field of sustainable biomass waste management, this work may also be of interest to those active in the field of carbon emission reductions. We summarize the potential of mitigating CO2 in a mineralisation step involving biomass residues, and the implications for CO2 capture and utilisation (CCU) to produce construction products from both solid and gaseous wastes. This work contributes to the development of sustainable value-added lower embodied carbon products from solid waste. The approach will offer reduced carbon emissions and lower pressure on natural resources (e.g. virgin stone, soil etc.)

Offsetting anthropogenic carbon emissions from biomass waste and mineralised carbon dioxide

The present work investigates biomass wastes and their ashes for re-use in combination with mineralised CO2 in cement-bound construction products. A range of biomass residues (e.g., wood derived, nut shells, fibres, and fruit peels) sourced in India, Africa and the UK were ashed and exposed to CO2 gas. These CO2-reactive ashes could mineralise CO2 gas and be used to cement ‘raw’ biomass in solid carbonated monolithic composites. The CO2 sequestered in ashes (125–414 g CO2/kg) and that emitted after incineration (400–500 g CO2/kg) was within the same range (w/w). The CO2-reactive ashes embodied significant amounts of CO2 (147–424 g equivalent CO2/kg ash). Selected ashes were combined with raw biomass and Portland Cement, CEM 1 and exposed to CO2. The use of CEM 1 in the carbonated products was offset by the CO2 mineralised (i.e. samples were ‘carbon negative’, even when 10% w/w CEM 1 was used); furthermore, biomass ashes were a suitable substitute for CEM 1 up to 50% w/w. The approach is conceptually simple, scalable, and can be applicable to a wide range of biomass ashes in a closed ‘emission-capture’ process ‘loop’. An extrapolation of potential for CO2 offset in Europe provides an estimate of CO2 sequestration potential to 2030

Utilization of Iron Ore Tailings for Brick Manufacture from Donimalai Mines of Karnataka, India

Mixing iron tailings with cement, sand and sodium silicate for manufacturing bricks was studied with the objective of converting the iron ore tailing waste into value-added products. Bricks were prepared using different compositions of iron tailings with proportions of Ordinary Portland Cement, sodium silicate and sand in cuboid mould (9″ X 5″X 3″). Bricks were air dried for 24 hours, placed in oven for 115 ± 10 °C for 24 hours. Mechanical properties such as compressive strength (CS), water absorption (WA), and efflorescence were measured. The maximum CS of 8.58 N/mm2 was recorded for tailing and cement ratios of 8:2. However, for making it more economical the ratio of 9:1 was considered and this compares very well with the Indian standard (IS): 3495 (Part 1) (1992) of bricks. The results also indicated that the tailing percentage in the bricks affects their mechanical properties. The WA rates of the manufactured bricks are low compared to standard fired clay bricks, and the same varies with process parameters. The low capillary pore may deter the formation of efflorescence. The process, with standardized parameters, may be commercially adapted, and large quantities of iron ore tailings may be put to use in making bricks. Thus, the process technology observed in this paper can potentially convert the huge amount of environmentally hazardous waste into value added product. Iron ore tailing may materialize as a sustainable supplement to soil's clay, use of which in brick making is restricted. The finding also usher a new area of research

Utilization of Iron Ore Tailings for Brick Manufacture from Donimalai Mines of Karnataka, India

210-220The iron tailings were mixed in various proportions with different combinations of cement, sand, and sodium silicate to obtain or value-added product out of iron tailing waste which is suitable for use in the construction industry. Bricks were made using a variety of compositions of iron tailings, Ordinary Portland Cement, sodium silicate, and sand in cuboid mould (9″X 5″X 3″). The bricks were dried for 24 hours, and then kilned at 115 ± 10°C for 24 hours. Mechanical features such as water absorption, compressive strength, and efflorescence are tested. The maximum compressive strength rating of 8.58 N/mm2 was recorded with ratios of 8:2 (Iron tailing and cement). However, in process of making it economical, the ratio of 9:1 has opted and this ratio complies with the requirement of the Indian standard (IS: 1077:1992) of the common burnt clay building bricks. Water absorption for the proposed bricks is less than that of burnt clay bricks. The lower capillary pore can prevent the formation of efflorescence. This process, with the same parameters, can be exchanged commercially, and a large number of wastes of iron ore can be used to make bricks. Therefore, the technological processes identified in this paper can convert large amounts of hazardous waste into the environment into value-added products. Iron tailing can be seen as a stable addition to clay soils, its use when restricted to making bricks. This research helps to open a new area of research

Soil carbon development in rejuvenated Indian coal mine spoil

The impact of mine spoil on the landscape is significant, as excavated rock-debris is commonly disposedin heaps that blanket the original land surface. Spoil heaps destroy the original soil habitat releasing soil-bound carbon, which is difficult to re-estate when mining operations cease and restoration begins. Thepresent work follows the development of vegetative cover on a coalmine spoil tip in India over a period of19 years following restoration. The potential of re-vegetated the mine spoil to imbibe carbon is examinedthrough the development of above- and below-ground biomass development. It was observed that the soilorganic carbon and microbial biomass carbon (MBC) significantly increased with re-vegetation age, withabove ground biomass increasing by 23 times, and belowground biomass increased by 26 times during theperiod of study. Soil organic carbon and MBC increased by 4× and 6.6× times, respectively. The averagecalculated annual carbon budget was 8.40 T/ha/year, of which 2.14 T/ha was allocated to above groundbiomass, 0.31 T/ha to belowground biomass, 2.88 T/ha to litter mass and 1.35 T/ha was sequestered intothe soil. This work has shown that the development of biomass following the restoration of mine spoilwas significant and that considerable quantities of carbon were stored in above and below ground plantmatter, and in the soil itself. It is concluded that appropriate restoration strategies can be used to rapidlyestablish a viable, healthy and sustainable ecosystem that imbibes carbon into former mine-impacted land

GEO-6 assessment for the pan-European region

Through this assessment, the authors and the United Nations Environment Programme (UNEP) secretariat are providing an objective evaluation and analysis of the pan-European environment designed to support environmental decision-making at multiple scales. In this assessment, the judgement of experts is applied to existing knowledge to provide scientifically credible answers to policy-relevant questions. These questions include, but are not limited to the following:• What is happening to the environment in the pan-European region and why?• What are the consequences for the environment and the human population in the pan-European region?• What is being done and how effective is it?• What are the prospects for the environment in the future?• What actions could be taken to achieve a more sustainable future?<br/

Sorption kinetics of zinc and nickel on modified chitosan

This study was conducted to evaluate the effect of equilibration time on adsorption of zinc [Zn(II)] and nickel [Ni(II)] on pure and modified chitosan beads. The initial adsorption of Zn(II) was high on molybdenum (Mo)-impregnated chitosan beads (MoCB) during the initial 60 min. However, after 240 min, Zn(II) adsorption occurred more on single super phosphate chitosan beads (SSPCB), followed by monocalcium phosphate chitosan beads (MCPCB), untreated pure chitosan beads (UCB), and MoCB. Similarly, Ni(II) adsorption was greatest on MoCB during the initial 60 min. At the conclusion of the experiment (at 240 min), the greatest adsorption was occurred on MCPCB, followed by MoCB, UCB, and SSPCB. Chemical sorption and intra-particle diffusion were probably the dominant processes responsible for Zn(II) and Ni(II) sorption onto chitosan beads. The results demonstrated that modified chitosan beads were effective in adsorbing Zn and Ni and hence, could be used for the removal of these toxic metals from soil

Carbon sequestration through plant reclamation in mined-out land : A Case Study

85-88The present study was aimed to evaluate the carbon sequestration potential of naturally and artificially revegetated reclaimed mine spoils. Carbon sequestration potential was measured in both types of mine spoils in terms of total plant biomass and microbial biomass carbon. It was observed that the artificially revegetated mine spoils have great potential to restore mineral contents, plant biomass and microbial biomass carbon, which increases along an age gradient of revegetated mine spoil and is comparatively higher than the naturally revegetated mine spoils. It was calculated through extrapolation that the organic carbon and plant biomass of an artificially revegetated mine spoil will reach the level of a native forest ecosystem in 26 and 34 years, respectively