Debate around increasing demand for natural resources is often framed in terms of a "nexus" and perhaps at risk of becoming a buzz word. A nexus between what, at what scales, and what would be the consequences? This article analyses why readers should care about the nexus concept towards the SDGs. We discuss a five-nodes definition and propose perspectives that may lead to a reload of climate policy with buy-in from supply chain managers and resourcerich developing countries. Our research perspectives address modelling approaches and scenarios at the interface of bio-physical inputs with the human dimensions of security and governance.

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Biorefinery, an example of a multiple products system, integrates biomass conversion processes and equipment to produce fuels, power and chemicals from biomass. This study focuses on technical design, economic and environmental analysis of a lignocellulosic feedstock (LCF) biorefinery producing ethanol, succinic acid, acetic acid and electricity. As the potential worldwide demand of succinic acid and its derivatives can reach 30 million tons per year, succinic acid is a promising high-value product if production cost and market price are substantially lowered. The results of the economic analysis show that the designed refinery has great potentials compared to the single-output ethanol plant; even when the price of succinic acid is lowered or the capital investment doubled. In terms of eco-efficiency, the LCF biorefinery shows better environmental performances mainly in global warming potential due to CO(2) fixation during acid fermentation. The overall evaluation of the eco-efficiency depends on the importance attached to each impact category.

Background, aim, and scope Facing the threat of oil depletion and climate change, a shift from fossil resources to renewables is ongoing to secure long-term low carbon energy supplies. In view of the carbon dioxide reduction targets agreed upon in the Kyoto protocol, bioethanol has become an attractive option for one energy application, as transport fuel. Many studies on the LCA of fuel ethanol have been conducted, and the results vary to a large extent. In most of these studies, only one type of allocation is applied. However, the effect of allocation on outcomes is of crucial importance to LCA as a decision supporting tool. This is only addressed in a few studies to a limited extent. Moreover, most of the studies mainly focus on fossil energy use and GHG emissions. In this paper, a case study is presented wherein a more complete set of impact categories is used. Land use has been left out of account as only hectare data would be given which is obviously dominated by agriculture. Moreover, different allocation methods are applied to assess the sensitivity of the outcomes for allocation choices. Materials and methods This study focuses on the comparison of LCA results from the application of different allocation methods by presenting an LCA of gasoline and ethanol as fuels and with two types of blends of gasoline with ethanol, all used in a midsize car. As a main secondgeneration application growing fast in the USA, corn stover-based ethanol is chosen as a case study. The life cycles of the fuels include gasoline production, corn and stover agriculture, cellulosic ethanol production, blending ethanol with gasoline to produce E10 (10% of ethanol) and E85 (85% of ethanol), and finally the use of gasoline, E10, E85, and ethanol. In this study, a substantially broader set of eight environmental impacts is covered. Results LCA results appear to be largely dependent on the allocation methods rendered. The level of abiotic depletion and ozone layer depletion decrease when replacing gasoline by ethanol fuels, irrespective of the allocation method applied, while the rest of the impacts except global warming potential are larger. The results show a reduction of global warming potential when mass/energy allocation is applied; in the case of economic allocation, it gives contrary results. In the expanded systems, global warming potential is significantly reduced comparing to the ones from the allocated systems. A contribution analysis shows that car driving, electricity use for cellulase enzyme production, and ethanol conversion contribute largely to global warming potential from the life cycle of ethanol fuels. Discussion The reason why the results of global warming potential show a reverse trend is that the corn/stover allocation ratio shifts from 7.5 to 1.7 when shifting from economic allocation to mass/energy allocation. When mass/energy allocation is applied, both more credits (CO 2 uptake) and more penalties (N 2 O emission) in agriculture are allocated to stover compared to the case of economic allocation. However, mo...

This study provides scenarios toward 2050 for the demand of five metals in electricity production, cars, and electronic appliances. The metals considered are copper, tantalum, neodymium, cobalt, and lithium. The study shows how highly technology-specific data on products and material flows can be used in integrated assessment models to assess global resource and metal demand. We use the Shared Socio-economic Pathways as implemented by the IMAGE integrated assessment model as a starting point. This allows us to translate information on the use of electronic appliances, cars, and renewable energy technologies into quantitative data on metal flows, through application of metal content estimates in combination with a dynamic stock model. Results show that total demand for copper, neodymium, and tantalum might increase by a factor of roughly 2 to 3.2, mostly as a result of population and GDP growth. The demand for lithium and cobalt is expected to increase much more, by a factor 10 to more than 20, as a result of future (hybrid) electric car purchases. This means that not just demographics, but also climate policies can strongly increase metal demand. This shows the importance of studying the issues of climate change and resource depletion together, in one modeling framework.

Today, almost 70% of the electricity is produced from fossil fuels and power generation accounts for over 40% of global CO 2 emissions. If the targets to reduce climate change are to be met, substantial reductions in emissions are necessary. Compared to other sectors emission reductions in the power sector are relatively easy to achieve because it consists mainly of point-sources. Carbon Capture and Storage (CCS) and the use of low-carbon alternative energy sources are the two categories of options to reduce CO 2 emissions. However, for both options additional infrastructure and equipment is needed. This article compares CO 2 emissions and metal requirements of different low-carbon power generation technologies on the basis of Life Cycle Assessment. We analyze the most critical output (CO 2 ) and the most critical input (metals) in the same methodological framework. CO 2 emissions and metal requirements are compared with annual global emissions and annual production for different metals. It was found that all technologies are very effective in reducing CO 2 emissions. However, CCS and especially non-fossil technologies are substantially more metal intensive than existing power generation. A transition to a low-carbon based power generation would require a substantial upscaling of current mining of several metals.

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The massive migration flows from rural to urban areas in China, combined with an expected decline in the total population over the next decades, leads to two important challenges for China's housing: the growth of its urban housing stock and the shrinkage of rural housing. The rural and urban housing systems in China were analyzed using a dynamic material flow analysis model for the period 1900-2100 for several scenarios assuming different development paths for population, urbanization, housing demand per capita, and building lifetime. The simulation results indicate that new housing construction is likely to decline for several decades due to the fast growth over the past 30 years and the expected increased longevity of dwellings. Such an oscillation of new construction activity would have significant implications for the construction industry, employment, raw material demand, and greenhouse gas emissions to produce the construction materials. Policy and practical options for mitigating the negative impacts are considered.