Abstract

The global warming is directly related to the increased greenhouse gas emissions from both natural and anthropogenic origins. There has been a drastic rise in the concentration of CO2 and other greenhouse gases since the industrial revolution primarily due to the intensifying consumption of fossil fuels. With the need to reduce carbon emissions and mitigate global warming certain strategies relating to carbon capturing and sequestration are indispensable. This paper comprehensively describes several physicochemical, biological and geological routes for carbon capture and sequestration. The trend of the increase in greenhouse gases over the years is illustrated along with the global statistics for fossil fuels usage and biofuels production. The physicochemical carbon capturing technologies discussed include absorption, adsorption, membrane separation and cryogenic distillation. The algal and bacterial systems, dedicated energy crops and coalbed methanogenesis have been vividly explained as the biological routes for carbon sequestration. The geological carbon sequestering route centers on biochar application and oceanic carbon storage. A systematic survey has been made on the origin and impact of greenhouse gases along with the potential for sequestration based on some fast-track and long-term sequestration technologies.

Abstract

The future roles of biomass and carbohydrate for meeting needs of food/feed, renewable materials, and transportation fuels (biofuels) remain controversial due to numerous issues, such as increasing food and feed needs, constraints of natural resources (land, water, phosphate, biomass, etc.), and limitations of natural photosynthesis, as well as competing energy conversion pathways and technologies. The goal of this opinion article is to clarify the future roles of biomass and biorefineries using quantitative data other than adjective words. In most scenarios, human beings could have enough biomass resource from plant photosynthesis for meeting the three goals at the same time: feeding 9 billion people, providing renewable materials, and producing transportation biofuels that could replace nearly all fossil fuel-based liquid fuels used in the land transportation in 2050. Land transport means will pass through transitions from internal combustion engines plus liquid fuels, to hybrid systems, to hydrogen fuel cell vehicles (FCVs), while battery electric vehicles (BEVs) could play a minor role. Next generation biorefineries based on artificial photosynthesis featuring ultra-high energy efficiency and low-water consumption could produce a large amount of carbohydrate and/or other biocommodities from hydrogen/electricity and CO2. In conclusion, it is time to develop next generation biorefineries, which will efficiently utilize nonfood biomass for the coproduction of multiple products from biofuels, biochemicals, to food/feed, and even store electricity/hydrogen by fixing CO2 to carbon-containing chemicals and biofuels. Next generation biorefineries will address the food, biofuels, and environment trilemma at the same time.