Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for ...millennia whereas other SOM decomposes readily--and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The mining of soluble potassium salts (potash) is essential for manufacturing fertilizers required to ensure continuous production of crops and hence global food security. As of 2014, potash is mined ...predominantly in the northern hemisphere, where large deposits occur. Production tonnage and prices do not take into account the needs of the farmers of the poorest countries. Consequently, soils of some regions of the southern hemisphere are currently being depleted of potassium due to the expansion and intensification of agriculture coupled with the lack of affordable potash. Moving away from mined salts towards locally available resources of potassium, such as K-bearing silicates, could be one option to improve this situation. Overall, the global potash production system and its sustainability warrant discussion. In this contribution we examine the history of potash production and discuss the different sources and technologies used throughout the centuries. In particular, we highlight the political and economic conditions that favored the development of one specific technology over another. We identified a pattern of needs driving innovation. We show that as needs evolved throughout history, alternatives to soluble salts have been used to obtain K-fertilizers. Those alternatives may meet the incoming needs of our century, providing the regulatory and advisory practices that prevailed in the 20th century are revised.
•The development of the potash industry from 1700 to the present days is reviewed.•A historical analysis reveals the origin of the current limitations of the potash market.•Past experiences provide guidelines for the successful development of a new generation of potash fertilizers.
Enhanced silicate rock weathering for long-term carbon dioxide sequestration has considerable potential, but depends on the availability of suitable rocks coupled with proximity to suitable locations ...for field application. In this paper, we investigate the established mining industry that extracts basaltic rocks for construction from the Paraná Basin, Sao Paulo State, Brazil. Through a Life Cycle Assessment, we determine the balance of carbon dioxide emissions involved in the use of this material, the relative contribution of soil carbonation and enhanced weathering, and the potential carbon dioxide removal of Sao Paulo agricultural land through enhanced weathering of basalt rock.
Our results show that enhanced weathering and carbonation respectively emit around 75 and 135 kg carbon dioxide equivalent per tonne of carbon dioxide equivalent removed (considering a quarry to field distance of 65 km). We underline transportation as the principal process negatively affecting the practice and uncover a limiting road travel distance from the quarry to the field of 540 ± 65 km for carbonation and 990 ± 116 km for enhanced weathering, above which the emissions offset the potential capture. Regarding Sao Paulo State, the application of crushed basalt at 1 t/ha to all of the State's 12 million hectares of agricultural land could capture around 1.3 to 2.4 Mt carbon dioxide equivalent through carbonation and enhanced weathering, respectively.
This study suggests a lower sequestration estimate than previous studies and emphasizes the need to consider all process stages through a Life Cycle Assessment methodology, to provide more reliable estimates of the sequestration potential of greenhouse gas removal technologies.
•First assessment of the burdens associated with enhanced weathering and carbonation.•Transportation of the material greatly impacts the sequestration potential.•The quarry to field offsetting distance is 550 ± 65 km for carbonation.•On Sao Paulo average, the practice emit 0.110 kg CO2 eq per kg of CO2 removed.•The setup burdens of the practice reduce previous sequestration estimates.
Recently published assessments of nutrient budgets on a national basis have shown that K deficits for developing countries are so substantial that a doubling of world production of potash fertilisers ...would be required to balance inputs and offtake, simply to meet demands in Africa alone. The price of potassium fertiliser raw materials has increased by a factor of 4 during 2007–2009, approaching $1000 per tonne in some markets. Thus an annual investment of the order of US$5600 million is required to replenish soil K stocks in Africa. In this context it is appropriate to review current knowledge of alternative sources of K, which is the seventh most abundant element in the Earth’s continental crust, present in feldspars and (much less commonly) feldspathoid minerals including nepheline and leucite. Theoretical considerations based on the experimental determination of mineral dissolution rates indicate that nepheline dissolves 100 times more quickly than potassium feldspar, and this suggests that nepheline-bearing rocks are more effective as sources of K for plant growth than granitic rocks, even though these have higher K contents. Crop trials with silicate rocks and minerals as sources of K show increased K availability and uptake for nepheline-bearing rocks compared with granitic rocks. Under conditions where soils are rapidly leached (especially tropical soils such as oxisols that contain quartz, aluminium oxy-hydroxides and kaolinite), with low capacity to retain soluble nutrients, the use of potassium feldspar or crushed granite does give a yield response, although no greater than for conventional fertilisers. In other experiments with crushed ultramafic, basaltic and andesitic rocks improvements in crop yield are claimed, although this cannot be unambiguously related to the mineralogical or chemical composition of the rock used. In conclusion, the present high cost of conventional potassium fertilisers justifies further investigation of potassium silicate minerals and their host rocks (which in some cases include basic rocks, such as basalt) as alternative sources of K, especially for systems with highly weathered soils that lack a significant cation exchange capacity. Such soils commonly occur in developing countries, and so this approach provides an opportunity to develop indigenous silicate rock sources of K as an alternative to sometimes prohibitively expensive commercial fertilisers.
Photosynthetic removal of CO2 from the atmosphere is an important planetary carbon dioxide removal mechanism. Naturally, an amount equivalent to all atmospheric carbon passes through the coupled ...plant–soil system within 7 years. Plants cycle up to 40% of photosynthesized carbon through their roots, providing a flux of C at depth into the soil system. Root-exuded carboxylic acids have the potential to supply 4–5 micromoles C hr–1g–1 fresh weight to the soil solution, and enhance silicate mineral weathering. Ultimately, the final product of these root-driven processes is CO2, present in solution as bicarbonate. This combines with Ca liberated by corrosion associated with silicate mineral weathering to enter the soil–water system and to produce pedogenic calcium carbonate precipitates. Combining understanding of photosynthesis and plant root physiology with knowledge of mineral weathering provides an opportunity to design artificial soils or to plan land use in ways that maximize removal and sequestration of atmospheric CO2 through artificially enhanced pedogenic carbonate precipitation. This process requires relatively low energy and infrastructure inputs. It offers a sustainable carbon dioxide removal mechanism analogous to the use of constructed wetlands for the passive remediation of contaminated waters, and is likely to achieve wide public acceptance.
Rapid urbanisation, with associated housing and infrastructure demands, leads to increased mining and use of non-renewable mineral raw materials needed for the construction industry including ...concrete and cement. In an emerging economy, like Thailand, which is part of Association of Southeast Asian Nations (ASEAN), current environmental management policies are insufficient to reduce raw material requirements or waste from demolition by generating inputs to construction through reuse or recycling. As part of the European Union (EU), Great Britain has successfully implemented integrated policies and achieved high rates of recycled aggregates in construction (29%) and a 70% reuse and recycling target for construction and demolition (C&D) waste. In this paper, Material Flow Analysis (MFA) of cement/concrete materials is combined with an interpretation of related policies to provide a deeper understanding how to achieve more sustainable management of natural resources. A comparative MFA for the construction industry in Great Britain and Thailand (representing an ASEAN country) has been developed that quantifies raw material inputs, buildings and infrastructure outputs, so that the practices in the two countries can be contrasted. We report domestic cement production and import/export data, and calculate the raw materials needed for cement and its calcination process for concrete production. Considering the most relevant policies and taxation in Great Britain, we identify possible ways forward for Thailand by introducing new policies and taxation that will have positive effects on raw material extraction, processing, construction and disposal practices and disposal behaviors. Following the MFA and policy analysis, we believe that similar benefits apply to other emerging economies.
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•Describes policies to provide a deeper understanding how to achieve more sustainable management of mined resources in the construction sector.•Reports domestic cement production and import/export data, and calculate the raw materials needed for cement and its calcination process for concrete production.•A comparative MFA for the construction industry in EU (Great Britain) and emerging economy (Thailand, representing an ASEAN country), has been developed.•Quantifies raw material inputs, buildings and infrastructure outputs, so that the practices in the two countries can be contrasted.•Identifies policies that can help other countries to reduce the disposal of non-renewable natural and mined resources.•More widely, similar approaches and policies will influence sustainable resource and waste management in other emerging economies.
The availability of K, essential for plant growth, from syenite (a silicate rock in which potassium feldspar is the dominant mineral; >90wt%), and phlogopite mica has been demonstrated using ...carefully designed plant growth pot experiments in which the only added source of K was the mineral of interest, with no loss of nutrients through drainage. Using pure quartz sand as a soil, both growth (increase in diameter) of leek plants and K-content of the plant material showed a dose-dependent positive response to the application (114–43000mgK/pot) of milled syenite with increases in plant diameter of 0.5–0.7mm/week, increasing with application rate. Phlogopite mica (114–6000mgK/pot) supported the highest observed increase in diameter (approx. 1mm/week) and plant K-content, both similar to that observed for a positive control (KCl). These experiments demonstrate that plants can obtain K for growth from milled syenite, in which feldspar is the dominant K-bearing mineral, and confirm previous observations that micas can be an effective source of K.
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•Plant growth in artificial soil has derived K from potassium feldspar as well as mica.•Use of mica (phlogopite) as a source of K gives response similar to KCl control.•The observed growth response in both cases increases with increasing mineral dose.•K content in plant tissue increases with dose, and confirms a mineral source for K.•The results highlight the potential of feldspar, in syenite rock, as a source of K for tropical soils.
Rapid Removal of Atmospheric CO2 by Urban Soils Washbourne, Carla-Leanne; Lopez-Capel, Elisa; Renforth, Phil ...
Environmental science & technology,
05/2015, Letnik:
49, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The measured calcium carbonate content of soils to a depth of 100 mm at a large urban development site has increased over 18 months at a rate that corresponds to the sequestration of 85 t of CO2/ha ...(8.5 kg of CO2 m–2) annually. This is a consequence of rapid weathering of calcium silicate and hydroxide minerals derived from the demolition of concrete structures, which releases Ca that combines with CO2 ultimately derived from the atmosphere, precipitating as calcite. Stable isotope data confirm an atmospheric origin for carbonate carbon, and 14C dating indicates the predominance of modern carbon in the pedogenic calcite. Trial pits show that carbonation extends to depths of ≥1 m. Work at other sites shows that the occurrence of pedogenic carbonates is widespread in artificially created urban soils containing Ca and Mg silicate minerals. Appropriate management of fewer than 12000 ha of urban land to maximize calcite precipitation has the potential to remove 1 million t of CO2 from the atmosphere annually. The maximal global potential is estimated to be approximately 700–1200 Mt of CO2 per year (representing 2.0–3.7% of total emissions from fossil fuel combustion) based on current rates of production of industry-derived Ca- and Mg-bearing materials.
The United Nations Sustainable Development Agenda 2030 calls for a transformative action to eradicate hunger and poverty and is particularly important for food production in developing countries (see ...SDG 1 Zero Hunger). Farmers in developing countries apply less potassium fertiliser than those in developed countries due to the high cost of imports and unavailability of domestic supplies. A circular economy approach can improve the efficient use of potassium resources throughout their life cycle from “mine to mouth” by identifying problem areas and assisting in designing supply strategies that help address the needs of farmers. As a nutrient, potassium conventionally follows a linear life cycle from mining. Using secondary data sources and literature, we analyse global demand and supply of potassium to quantify and illustrate the major supply shortages in the Global South.
This study identifies six options to improve potassium availability: (1) expanding conventional potassium mining and distribution systems serves those who can afford globally-traded fertiliser products; (2) seeking alternative sources of potassium, such as remineralisers, that provide a local source that is accessible to poorer farmers, and in many cases helps the circular economy of local mining operations that focus on other products; (3) improving markets by supporting trade and mitigating some of the disadvantages encountered in developing countries, such as transport and small scale of purchasing; (4) increasing the use of organic fertilisers, such as sewage and manures; (5) reusing crop residues and other farm wastes as sources of potassium, regarding a farm unit as a closed system as far as is practicable; and (6) recycling food waste so that nutrients return to the land, rather than to discard. Existing restrictions and practices mean that there is no single solution to enhance food production in the Global South using the circular economy principles. However, if these circular economy principles and policies are considered at farm to country scale progress can be made.
•Poor availability of potassium and soil leaching in developing countries requires new approaches to nutrient management.•New nutrient management actions should be aligned with the circular economy principles.•Six approaches to improve the supply, application and recovery of potassium fertilisers are proposed.•The paper discusses the challenges and limitations of scaling up some of the approaches.•Early progress includes use of crushed rock fines, previously seen as wastes, as remineralizers.
The role of organoclays in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clays used ...for this study were Na-montmorillonite and saponite. These two clays were treated with didecyldimethylammonium bromide to produce organoclays which were used in this study. The study indicated that clays with high cation exchange capacity (CEC) such as Na-montmorillonite produced an organomontmorillonite that was inhibitory to biodegradation of the crude oil hydrocarbons. Extensive hydrophobic interaction between the organic phase of the organoclay and the crude oil hydrocarbons is suggested to render the hydrocarbons unavailable for biodegradation. However, untreated Na-montmorillonite was stimulatory to biodegradation of the hydrocarbons and is believed to have done so because of its high surface area for the accumulation of microbes and nutrients making it easy for the microbes to access the nutrients. This study indicates that unlike unmodified montmorillonites, organomontmorillonite may not serve any useful purpose in the bioremediation of crude oil spill sites where hydrocarbon removal by biodegradation is desired within a rapid time period.
•Organomontmorillonite is inhibitory to biodegradation of crude oil hydrocarbons.•Unmodified montmorillonite stimulates biodegradation of crude oil hydrocarbons.•Adsorption of crude oil hydrocarbons during biodegradation is significant.•Unmodified saponite neither inhibits nor enhances biodegradation of hydrocarbons.
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