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Sugarcane mills currently use sugarcane bagasse to cogenerate heat and electricity, supplying the process with mechanical, thermal and electrical energy. Some of these plants are able to produce surplus electricity to export to the national grid. With the improvement in collection techniques, sugarcane straw has also become available and has been used in some mills as fuel for steam boilers, mixed with sugarcane bagasse. However, due to different traits compared to bagasse, the use of sugarcane straw may pose additional problems of incrustation and corrosion on heat exchange surfaces. Several alternatives and technologies have been studied and tried out in order to increase the production of surplus electricity. Among others, biomass integrated gasifier–gas turbine combined cycle (BIGCC) is a promising technology. However, several attempts have resulted in failure, whether on a pilot or industrial scale. Biomass gasification integrated with internal combustion engines can become an opportunity for generation of small power capacity (<15 MW) and integrated to sugarcane mills. This paper analyzes the difficulties and barriers to increasing electricity generation in the sugarcane industry through studies, projects and experimental and industrial-scale installations that have already been carried out. • Bagasse and cane straw show great potential for electricity generation. • Sugarcane industry in Brazil accounts for 6.4% of the electricity generated. • Biomass integrated gasification and combined cycle can increase electricity generation. • Technological and economic challenges are major barriers to the development of BIGCC. • No BIGCC project already implemented is currently in commercial operation. [ABSTRACT FROM AUTHOR]

The biorefinery concept provides a wide perspective of products and uses from the biomass conversion. The drive for cost reductions and the threat of food competition have put residual biomass under the spotlight. Sugarcane is the most produced crop in the world, and its residual bagasse has got the additional feature of abundance. Going beyond its traditional use for electricity and thermal generation, this paper explores the potential alternative uses for the sugarcane bagasse in Brazil. Under an Input-Output perspective, Brazilian production recipes are obtained for six distinct biorefining technologies assuming the use of sugarcane bagasse as feedstock. Also, minimum selling prices are derived for the main products of each technological route assessed, comprising an initial estimative of their cost prices in Brazil. The biomass to ethanol and higher alcohol route presented the higher share (25%) of productive and service sectors into its production recipe. The bioplatform succinic acid route was the only one reaching competitive minimum selling prices (0.57 US$/kg) in comparison to current pricing of the fossil-derived succinic acid. [ABSTRACT FROM AUTHOR]

The potential for sugarcane ethanol from Brazil to mitigate GHG emissions is undeniable, but the way that ethanol is produced during the agricultural and industrial phases will ultimately determine its benefits to society. In this paper, we evaluate the environmental impacts of sugarcane agriculture and ethanol production in Brazil as management practices continue to change and production expands to new frontiers. We focused our evaluation on the impacts on water, atmosphere, and soils, including how the application of organic and inorganic fertilizers and the accumulation of crop residue in the field affect emissions of greenhouse gases (GHG). We also addressed the impacts of land use changes on threatened biomes and discussed some of the present obstacles regarding conservation and restoration efforts. We concluded that, since a similar assessment was put forth in 2008, our knowledge about the environmental impacts of sugarcane ethanol in Brazil has advanced with regard to soil degradation, nitrogen dynamics, and soil carbon stocks. However, more information is still needed about the impacts of the increasing use of pesticides, herbicides, and fertilizers in sugarcane agriculture, especially on water resources. Furthermore, without a better understanding about how landscape fragmentation affects the biodiversity of terrestrial and aquatic tropical ecosystems and the services they provide, policies created to protect and restore them may be ineffective. On the other hand, the use of presently available scientific information to end unsustainable farming and the implementation of conservation strategies proposed by the Brazilian Forest Code could be a first step to guarantee that ethanol is produced more sustainably in Brazil. [ABSTRACT FROM AUTHOR]

The replacement of fossil fuels by biofuels has been extremely important worldwide to stimulate the growth of economies based on the sustainability through the use of renewable resources. Anaerobic digestion for biogas production is recognized as a clean technology that allies the suitability of wastes with energy generation, fulfilling the requirements for a sustainable alternative to provide the optimization of the biofuels production. This alternative is especially interesting for the sugarcane ethanol production in Brazil, in which the generation of vinasse, the main liquid waste, is very expressive. Nevertheless, the use of vinasse for anaerobic digestion has been finding some challenges to its establishment in the Brazilian sugarcane biorefineries. This paper reviews the actual context of anaerobic digestion within the sugarcane ethanol production in Brazil, presenting the main obstacles for its full application and the directions to promote it as well. Alternatives for biogas use are also presented and compared, highlighting the environmental and energy advantages of applying anaerobic digestion in the sugarcane biorefineries. This scenario is envisaged as a suitable way to achieve the future biorefineries model, based on the use and recovery of renewable resources with economic, social, and environmental benefits. [ABSTRACT FROM AUTHOR]

This paper presents the potential of biogas from anaerobic digestion of vinasse and its impact in different contexts. The use of vinasse biogas (VBG) for power generation is evaluated and the potential of this energy source is compared with fossil oil power plants in terms of energy, costs and greenhouse gases (GHG) emissions in Brazil, suggesting a program where the most expensive oil power plants are replaced by biogas plants with benefits in all aspects. Secondly, the use of vinasse biomethane (VBM) to replace natural gas (NG) in the state of São Paulo is examined, presenting an incentive program that could make this alternative fuel feasible even in smaller scale plants with minimal impact on NG costs in this state, while providing considerable emission reduction. The impact of VBG considering the increase in ethanol production over the next ten years is also evaluated, showing that substantial additional energy can be obtained and larger amounts of fossil fuels can be replaced. By crossing vinasse biogas potential with selected fossil fuels demand, the article brings insights to help the transition to a low-carbon society in a novel approach. The conclusions are that VBG and VBM can provide great benefits, such as USD 1 billion/year cost reductions and 6.7 million tons CO 2e /year emissions avoided by replacing fossil oil by biogas in power generation in Brazil and 3.2 million tons CO 2e /year avoided with biomethane replacing natural gas in the state of São Paulo, which, with specific programs and policies, could be achieved. • Vinasse biogas could replace fossil oil and natural gas in Brazil. • Electricity from vinasse biogas avoid GHG emissions at lower costs than oil plants. • Vinasse biomethane can replace natural gas in São Paulo with minimal cost increase. • Vinasse biogas can substitute more fossil fuels with increased ethanol production. [ABSTRACT FROM AUTHOR]

There have been many efforts to improve sugarcane cultivation and conversion technologies in the ethanol industry. In this study, an economic assessment and greenhouse gas (GHG) emissions analysis are performed on ethanol produced conventionally from sugarcane sugar and on an emerging process where the sugarcane bagasse is additionally used to produce ethanol. The combined conventional plus lignocellulosic ethanol pathway is found to be less economically favorable than the conventional ethanol pathway unless a series of technical challenges associated with cost reductions in lignocellulosic ethanol production are overcome, reaching a production cost at 0.31 $/L. This is expected to be achieved in a prospective 2020 scenario. GHG emissions savings against gasoline for both the conventional ethanol and the conventional plus lignocellulosic ethanol pathways are confirmed and found to increase with technological developments projected to occur over time. However, the absolute numbers are highly sensitive to the way of claiming credits from surplus electricity co-generated in the mill. These are 86%, 110% and 150% for the conventional ethanol in the 2020 scenario when the surplus electricity is assumed to replace the average electricity, the ‘combined-sources’ based electricity and the marginal electricity, respectively. For the conventional plus lignocellulosic ethanol pathway, they are 80%, 85% and 95% respectively in the 2020 scenario. Finally, a series of sensitivity analyses found the comparison in the GHG emissions between the two production pathways is not sensitive to changes in the sugarcane yield or the emissions factor for the enzymes used in the lignocellulosic ethanol process. However, the plant size is an influential factor on both the ethanol production cost (a lowest MESP of 0.26 $/L at the scale of 4 MM tonne cane/yr) and the GHG emission factors, partially because of the important role that transport of feedstock biomass (sugarcane and trash) plays in both elements. [ABSTRACT FROM AUTHOR]