• Energy Research
• 2021-2025close
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Management decisions concerning phosphorus (P) fertilization affect the profitability of crop production and potential water quality impairment. Soil testing for P provides a useful diagnostic framework to assess P bioavailability that informs management decisions to optimize P use in nutrient management and mitigate environmental impairment. Management factors such as tillage and P fertilization strategy can influence crop yield and the potential for soil and P losses with surface runoff. Investigation into which forms of soil and P losses that do occur from corn-soybean rotations in Iowa systems can inform which methodologies best quantify forms of P that will pose greater effects on water quality and which management decisions minimize losses while maintaining agronomic productivity. This research field calibrated a recently widely-adopted soil P test that uses weak organic acids with corn and soybean yield to identify critical soil-test P concentrations. The weak organic acids test extracted less soil P and performed more poorly than currently routine tests at relating soil-test P to crop yield. A second study was conducted to quantify the effect of P fertilization strategy and tillage on soil and P losses with runoff in a corn-soybean rotation in Northwest Iowa. Corn yield and soil loss were the highest with tillage, the combination of tillage and broadcast P resulted in the highest runoff TP loss, and the dissolved-reactive fraction of the total P loss was much higher with no-till. The combination of chisel-plow/disking and annual subsurface band placement of P fertilizer led to the lowest losses of dissolved-reactive P and total P, while optimizing crop yields. A third study compared multiple methods for measuring soluble P in runoff, and how management factors in Iowa cropping systems affect their performance. The results suggest that assuming only soluble, orthophosphate-P determined by colorimetric method may underestimate soluble P concentration in runoff and losses from crop fields and will be ...

The future performance of the widely abundant European beech (Fagus sylvatica L.) across its ecological amplitude is uncertain. Although beech is considered drought-sensitive and thus negatively affected by drought events, scientific evidence indicating increasing drought vulnerability under climate change on a cross-regional scale remains elusive. While evaluating changes in climate sensitivity of secondary growth offers a promising avenue, studies from productive, closed-canopy forests suffer from knowledge gaps, especially regarding the natural variability of climate sensitivity and how it relates to radial growth as an indicator of tree vitality. Since beech is sensitive to drought, we in this study use a drought index as a climate variable to account for the combined effects of temperature and water availability and explore how the drought sensitivity of secondary growth varies temporally in dependence on growth variability, growth trends, and climatic water availability across the species' ecological amplitude. Our results show that drought sensitivity is highly variable and non-stationary, though consistently higher at dry sites compared to moist sites. Increasing drought sensitivity can largely be explained by increasing climatic aridity, especially as it is exacerbated by climate change and trees' rank progression within forest communities, as (co-)dominant trees are more sensitive to extra-canopy climatic conditions than trees embedded in understories. However, during the driest periods of the 20th century, growth showed clear signs of being decoupled from climate. This may indicate fundamental changes in system behavior and be early-warning signals of decreasing drought tolerance. The multiple significant interaction terms in our model elucidate the complexity of European beech's drought sensitivity, which needs to be taken into consideration when assessing this species' response to climate change.

The over 15 million metric tonnes of carbon black produced annually emit carbon dioxide in the range of 29–79 million metric tonnes each year. With the renaissance of carbon black in many new renewable energy applications as well as the growing transportation sector, where carbon black is used as a rubber reinforcement agent in car tires, the carbon black market is expected to grow by 66% over the next 9 years. As such, it is important to better understand energy intensity and carbon dioxide emissions of carbon black production. In this work, the furnace black process is studied in detail using process models to provide insights into mass and energy balances, economics, and potential pathways for lowering the environmental impact of carbon black production. Current state-of-the-art carbon black facilities typically flare the tail gas of the carbon black reactor. While low in heating value, this tail gas contains considerable amounts of energy and flaring this tail gas leads to low overall efficiency (39.6%). The efficiency of the furnace black process can be improved if the tail gas is used to produce electricity. However, the high capital investment cost and increased operating costs make it difficult to operate electricity generation from the tail gas economically. Steam co-generation (together with electricity generation) on the other hand is shown to substantially improve energy efficiency as well as economics, provided that steam users are nearby. Steam co-generation can be achieved via back-pressure steam turbines so that the low-pressure exhaust steam (∼2 bar/120 °C) can be used locally for heating or drying purposes. Furthermore, the potential of utilizing hydrogen to reduce carbon dioxide emissions is investigated. Using hydrogen as fuel for the carbon black reactor instead of natural gas is shown to reduce the carbon dioxide footprint by 19%. However, current prices of hydrogen lead to a steep increase in the levelized cost of carbon black (47%).

AbstractIt is not known whether dietary guidelines proposing a limited intake of animal protein are compatible with the adoption of circular food systems. Using a resource-allocation model, we compared the effects of circularity on the supply of animal-source nutrients in Europe with the nutritional requirements of the EAT-Lancet reference diet. We found the two to be compatible in terms of total animal-source proteins but not specific animal-source foods; in particular, the EAT-Lancet guidelines recommend larger quantities of poultry meat over beef and pork, while a circular food system produces mainly milk, dairy-beef and pork. Compared with the EAT-Lancet reference diet, greenhouse gas emissions were reduced by up to 31% and arable land use reduced by up to 42%. Careful consideration of the feasible substitutability between animal-source foods is needed to define potential roles of animal products in circular human diets.