Water quality, temperature, and consumption are all potential concerns with biorefineries. Over time, as demand rises for limited freshwater supplies, these issues are likely to only become more important. Briefly, the issues are as follows:
- Water quantity: Any water savings results in a direct financial benefit to a mill and also addresses growing concerns over the availability of freshwater for other purposes (e.g. agriculture, human consumption).
- Water quality: It is of major concern for rare and endangered species, recreation, and for its effects on other users downstream (e.g. municipalities).
- Thermal discharge: The temperature of the cooling water discharge is also of concern for its effect on flora and fauna.
Depending on the configuration (amount of fuels and electricity produced), the biorefinery will have different effects on water quantity and thermal discharge at a mill, but overall the conversion to biorefineries is not expected to significantly impact water quality, especially when considering the impacts on displaced grid power (Larson et al. 2003). Also, IGCC power plant will reduce cooling water and make‐up water discharges locally at the mill, and because the efficient gasifiers will cause grid power reductions, substantial reductions in cooling water requirement at power plant will also occur (Larson et al. 2003). Overall, the implementation of IGCC power plant will cause net savings in cooling water requirements and net reductions in wastewater discharges. An additional benefit is also the avoided water usage in conventional fuel production, which has not been quantified. Moreover, the consequences of spills from petroleum and petroleum product transportation are also reduced. Also, some of the biofuels, namely DME and MA, pose much lower risks of groundwater contamination in the event of a fuel leak or spill (e.g. at refueling stations). FT liquids, since they contain very low aromatics, should also pose a lower risk than conventional diesel and gasoline.
Solid waste issues relate to the quantity and toxicity of any solids that must be disposed of. In this regard, biorefineries are not expected to result in significant changes at the mill, in part because the solids produced (mainly ash from biomass) are not problematic to deal with. There will be the need to periodically replace catalysts and guard beds, such as zinc oxide (for H2S) and activated carbon (for other trace contaminants). Nevertheless, as with water usage, the impacts of displaced grid power (particularly for the coal component of that grid power) and conventional transportation fuel use would likely result in important reductions of solid waste generation (Larson et al. 2003).
Mill‐Related Air Emissions
The most significant effluent differences between biorefineries and Tomlinson systems are expected to be in air emissions. This is particularly expected to be the case in a WTW context. As discussed below, air emissions were estimated in detail for both the biorefineries and the Tomlinson power/recovery systems. For comparison, the BLGCC case from our earlier study is also shown, with the updated assumptions consistent with the current analysis (e.g. grid power emissions). Actual air emissions data are available for modern Tomlinson systems. Since emissions data do not exist for BLGCC or biorefinery systems, estimates were made starting with data for coal IGCC and natural‐gas combined cycle power systems and adjusting appropriately. Note that relative to the BLGCC configuration, sources of air emissions in a biorefinery are expected to be similar, namely the power island. The production of the biofuel itself does not lead to significant additional sources of air emissions at the biorefinery.
The air emissions analysis presented below is not intended to serve as a complete lifecycle analysis of biorefinery emissions. Rather the estimates provide indicative results of the potential impacts of biorefinery options relative to “business as usual” in the pulp and paper industry. For example, upstream emissions for grid power (i.e. fuel production and transportation to the power plant) are not included, but these are relatively small compared to the power plant emissions themselves and to the total emissions from conventional motor fuel chains. To the extent that most of the biorefinery configurations result in more displaced grid power than the Tomlinson case, the emissions benefits estimated in this study can be considered conservative because they do not also factor in emissions reductions related to fuel supply for power plants.
Air emissions fall into three basic categories: criteria pollutants, hazardous air pollutants (HAPs), and GHGs. This study includes quantitative estimates for the criteria pollutants: sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), volatile organic compounds (VOCs), PM, and total reduced sulfur (TRS). Estimates are also made for carbon dioxide (CO2), the major greenhouse gas. HAPs and other emissions issues are discussed qualitatively.
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