Study: Renewables played crucial role in U.S. CO2 reductions

After a nearly 20-year upward trend, U.S. CO2 emissions from energy took a sharp and unexpected turn downwards in 2007. By 2013, the country’s annual CO2 emissions had decreased by 11% – a decline not witnessed since the 1979 oil crisis. Experts have generally attributed this decrease to the economic recession, and to a huge surge in cheap natural gas displacing coal in the U.S. energy mix. But those same experts mostly overlooked another key factor: the parallel rise in renewable energy production from sources like wind and solar, which expanded substantially over the same 2007-2013 timeframe. Between 2007 and 2013, wind generated electricity grew almost five-fold to 168 TWh and utility-scale solar from 0.6 TWh to 8.7 TWh. During the same period, bioenergy production grew 39 percent to 4,800 trillion BTUs. Given these increases, how much did renewables contribute to the emissions reductions in the United States? In a paper published this month in the journal Energy Policy, we use a method called decomposition analysis to answer just that

Turning the corner on US power sector CO2 emissions—a 1990–2015 state level analysis

Total CO2 emissions from the United States power sector increased over the period 1990–2005, but peaked soon after, and by 2015 they had declined by 20% compared to 2005. This study analyzes the supply-side drivers of the increasing trend up until 2005 as well as the factors across US states that enabled significant reductions in the following decade. Using index decomposition analysis, we show that the two main factors driving the CO2 decrease were natural gas substituting for coal and petroleum, and large increases in renewable energy generation (primarily wind)—which were responsible for 60% and 30% of the decline respectively since 2005. Both effects were concentrated in states where low natural gas prices or a combination of federal tax credits, state energy policies, decreasing costs of renewables, and advantageous wind conditions drove significant reductions of CO2 emissions—resulting in the overall national emissions decline

Decomposition Analysis And Renewables In CO2 Emission Trends

The decline in carbon dioxide emissions in the United States between 2007 and 2013 is actually more complex than previously thought. During that period, carbon dioxide emissions from United States energy use decreased sharply and unexpectedly, after rising for nearly two decades. At the end of the six-year period, U.S. annual carbon dioxide emissions had fallen by 11 percent– a drop the nation hadn’t experienced since the 1979 oil crisis. Experts have typically attributed this decline to two factors: the drop in energy demand during the recession that began in 2007 and the surge in inexpensive natural gas that displaced coal in the energy mix during the same time. However, they missed another critical influence that hastened the decline in emissions just as much: the rapid rise in renewable energy production. Between 2007 and 2013, wind-generated electricity grew nearly five times, to 168 terawatt hours, enough to power 15 million average American homes, while utility-scale solar grew to 8.7 TWh. During the same period, bioenergy production grew to 4,800 trillion BTUs, or 39 percent, which includes biofuels in the transportation sector

Factoring in the forgotten role of renewables in CO2 emission trends using decomposition analysis

This paper introduces an approach for separately quantifying the contributions from renewables in decomposition analysis. So far, decomposition analyses of the drivers of national CO2 emissions have typically considered the combined energy mix as an explanatory factor without an explicit consideration or separation of renewables. As the cost of renewables continues to decrease, it becomes increasingly relevant to track their role in CO2 emission trends. Index decomposition analysis, in particular, provides a simple approach for doing so using publicly available data. We look to the U.S. as a case study, highlighting differences with the more detailed but also more complex structural decomposition analysis. Between 2007 and 2013, U.S. CO2 emissions decreased by around 10%—a decline not seen since the oil crisis of 1979. Prior analyses have identified the shale gas boom and the economic recession as the main explanatory factors. However, by decomposing the fuel mix effect, we conclude that renewables played an equally important role as natural gas in reducing CO2 emissions between 2007 and 2013: renewables decreased total emissions by 2.3–3.3%, roughly matching the 2.5–3.6% contribution from the shift to natural gas, compared with 0.6–1.5% for nuclear energy

A targeted ultra performance liquid chromatography – Tandem mass spectrometric assay for tyrosine and metabolites in urine and plasma: Application to the effects of antibiotics on mice

International audienceTyrosine plays a key role in mammalian biochemistry and defects in its metabolism (e.g., tyrosinemia, alkaptonuria etc.) have significant adverse consequences for those affected if left untreated. In addition, gut bacterially-derived p-cresol and its metabolites are of interest as a result of various effects on host xenobiotic metabolism. A fit-for-purpose quantitative ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay was developed to target and quantify tyrosine and eleven metabolites in urine and plasma. Dansylation, using dansyl chloride, was used to improve chromatographic and mass spectral properties for tyrosine and nine phenolic metabolites, with detection using positive electrospray ionisation (ESI). The sulfate and glucuronide conjugates of p-cresol, where the phenol group was blocked, were quantified intact, using negative ESI via polarity switching during the same run. Sample preparation for urine and plasma involved deproteinization by solvent precipitation (of acetonitrile:isopropyl alcohol (1:1 v/v)) followed by in situ dansylation in 96 well plates. To minimize sample and solvent usage, and maximize sensitivity, analysis was performed using microbore reversed-phase gradient UPLC on a C8 phase with a 7.5 min. cycle time. The coefficients of variation obtained were <15%, with lower limits of quantification ranging from 5 to 250 nM depending upon the analyte. The method was applied to plasma and urine samples obtained from mice placed on a high tyrosine diet with one subgroup of animals subsequently receiving antibiotics to suppress the gut microbiota. Whilst plasma profiles were largely unaffected by antibiotic treatment clear reductions in the amount of p-cresol sulfate and p-cresol glucuronide excreted in the urine were observed for these mice