Biodiesel

UN report warns that a hasty switch to biofuels could have major impacts on livelihoods and the environment

The report warns of the impacts on nature: “Use of large-scale mono-cropping could lead to significant biodiversity loss, soil erosion and nutrient leaching.”

This has been avoided, the report says, in the Brazilian state of Sao Paulo where sugar cane farmers are obliged to leave a percentage of their land as natural reserves.

Water is also a concern. The expanding world population and the on-going switch towards consumption of meat and dairy produce as incomes rise are already putting pressure on freshwater supplies, which increased growing of biofuel crops could exacerbate.

In conclusion, UN Energy suggests policymakers should take a holistic look before embarking on drives to boost biofuel use.

“Only through a convergence of biodiversity, greenhouse gas emissions and water-use policies can bioenergy find its proper environmental context and agricultural scale,” the report concludes.

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Biodiesel wont drive down global warming

EU legislation to promote the uptake of biodiesel will not make any difference to global warming, and could potentially result in greater emissions of greenhouse gases than from conventional petroleum derived diesel. This is the conclusion of a new study reported in a recent article published in Chemistry & Industry, the magazine of SCI.

Analysts at SRI Consulting compared the emissions of greenhouse gases by the two fuels across their overall life cycles from production to combustion in cars.

The results show that biodiesel derived from rapeseed grown on dedicated farmland emits nearly the same amount of greenhouse gas emissions (defined as CO2 equivalents) per km driven as does conventional diesel.

However, if the land used to grow rapeseed was instead used to grow trees, petroleum diesel would emit only a third of the CO2 equivalent emissions as biodiesel.

Petroleum diesel emits 85% of its greenhouse gases at the final stage, when burnt in the engine. By contrast, two-thirds of the emissions produced by rapeseed derived biodiesel (RME) occur during farming of the crop, when cropland emits nitrous oxide (N2O), otherwise known as laughing gas, that is 200-300x as potent a greenhouse gas as CO2.

The results of this analysis should have big implications for policymakers. The 2003 EU Biofuels Directive aims to increase the levels of biofuels to 5.75% of all transport fuels by 2010, up from roughly 2% currently. This will be further increased to a 10% share in 2010, the Commission announced in January 2007.

Source: Chemistry & Industry

If you think biodiesel is green – think again

According to the bus company National Express - biofuels aren’t the green option.  The firm has recently announced that it is withdrawing from a biofuels trial after consulting with environmental groups and concluding, in the words of chief executive Richard Bowker, that “what appears to be the green option may not actually be green after all”.

Bowker said that while the fuels “may well have a role to play in helping us [National Express] reduce the emissions of greenhouse gases arising from transport operations in the future”, the company was not convinced of their green benefits at present.

National Express are not alone with their concerns. Environmental studies indicate that intensive farming methods can give biodiesel a bigger carbon footprint than traditional oil.

Yet not all biofuels are created equal. The way a fuel is manufactured can add greatly to its carbon impact. For example, if rainforest is cut down to make way for a biofuel soya plantation, it will release a lot of CO2 into the atmosphere. Intensive cropping may also contribute to the release of biogenic CO2 and other secondary pollutants like ozone. Then there are fertilisers to consider, which put nitrous oxides (powerful greenhouse gases) into the atmosphere, plus the carbon footprint associated with planting, irrigating, application of pesticides, harvesting, transportation, oilseed crushing and processing, plus the infrastructure required to deliver and administer a new type of fuel on the forecourt (in tandem with current fuel supplies).  And lastely, any additional CO2 associated with the manufacturing and modifications required to new and existing engines must also be included when calculating the carbon footprint.

If that seems a scandalous betrayal of the whole rationale behind biofuels, its because the US oilseed and biotech industries global promotion of biofuel is nothing to do with carbon, but more to do with clever consumer targeted marketing and corporate sponsorship.

The problem is that consumers assume “biofuel” automatically means “greener than conventional petrochemical fuels”. For this reason, environmental groups have been pressing the UK government to set binding standards so that all biofuels used in British vehicles deliver a minimum level of carbon reduction compared to conventional fuels.

Environmental groups have also lobbied the government to set standards on sustainability of biofuel plantations, to limit their adverse effects on wildlife habitats.

The government has responded: by 2010, the fuel blend at British pumps must contain 5% biofuel; minimum greenhouse gas standards for biofuels will be brought in the same year, with sustainability standards coming in the year afterwards.

So it would appear that some of these problems are in the process of being sorted out. But as usual, it’s the “cart before the horse” with environmental concerns once again being pushed aside in favour of biofuel marketing and corporate sponsorship.

There are other issues also - the fact that the growth of the biofuel industry is pushing up food prices in some places as traditional food crops are being replaced with crops like oilseed rape specifically grown by farmers who have bought into lucrative biofuel contracts.

Environmental groups do indeed regard biofuels as a good thing, provided they deliver confirmed greenhouse gas savings and are sustainably produced.

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Biodiesel Exhaust: The Need for Health Effects Research

Similar to other combustion emissions, biodiesel exhaust emissions contain irritant gases and vapors such as nitrogen oxides, aldehydes, and a wide range of organic compounds, some of which are also likely to present an oxidative stress (Mauderly 1997). The potential of biodiesel to form aldehydes is related to fuel quality. When used in a diesel engine, biodiesel with a high glycerol content (indicating poor post-transesterification refining) produces emissions with increased acrolein levels (Graboski and McCormick 1998). Ethanol and methanol—typical alcohols used in biodiesel production—are aldehyde precursors, and if not removed from the biodiesel could combust partially to form formaldehyde and acetaldehyde which are classified as a carcinogen and possible carcinogen, respectively [International Agency for Research on Cancer (IARC) 1985; McDonald and Spears 1997].

Biodiesel Exhaust Emissions and Human Health

There is insufficient information regarding the mutagenic potential of biodiesel emissions specific to fuel category (e.g., starting oil feed-stock), engine type, and operating conditions. In in vitro bacterial assays, most of the mutagenic activity in biodiesel exhaust is contributed by a minority of the soluble organic fraction mass, particularly PAHs (Mauderly 1997). To date only one published in vitro study has evaluated mutagenicity of biodiesel soluble organic fraction using a competent mammalian cell model (rat hepatocytes) in addition to the traditional Ames assay (Eckl et al. 1997). The authors observed in the Ames assay higher mutagenic potential in the diesel exhaust than in the rapeseed methyl ester (RME), but reported that the results observed were less dramatic in the rat hepatocyte model. They attribute this difference to the differences in metabolic capacities between the models.

The cytotoxic effects of biodiesel exhaust emissions have also been evaluated and compared to petroleum diesel fuel emissions (Bunger et al. 2000). Cytotoxic effects of biodiesel from RME emissions were greater than those of petroleum diesel fuel. Exhaust from rapeseed biodiesel was 4-fold more potent than petroleum diesel exhaust in inducing cytotoxicity (measured as the median effective dose; ED50). Cytotoxicity of biodiesel emissions increased with extract collected with the engine “idling.”

Although it can sometimes be difficult to place the results of animal investigation into the context of potential human health hazard, animal models are viewed to be superior to in vitro studies for establishing pulmonary and extrapulmonary responses to potentially toxic exposures (Finch et al. 2002). Subchronic exposure of rats to emissions from a diesel engine burning soybean oil–derived biodiesel fuel induced a dose-related increase in particle-containing alveolar macrophages—a consistent observation in rats subchronically exposed to petroleum diesel exhaust (Finch et al. 2002; Mauderly 1994). The vast majority of exposed rats had little or no evidence of lung neutrophilia and centriacinar fibrosis (Finch et al. 2002). Overall, the study concluded that there were neither significant differences from air exposed control group nor consistent exposure-related significant differences among most of the health parameters evaluated.

To date, only one epidemiologic study has been conducted in which the acute health effects from exposure to biodiesel exhaust fumes were assessed by a questionnaire given to workers who are typically exposed to diesel fumes (e.g., delivery truck drivers, road-maintenance workers, and industrial fork lift truck drivers) (Hasford et al. 1997). This investigation demonstrated dose-dependent respiratory symptoms after exposure to RME and diesel fumes, but there were no significant differences between the two fuels.

Research Needs Regarding Biodiesel Exhaust Emissions and Human Health

Although currently accounting for a small fraction of diesel use, biodiesel is a fuel alternative that has shown potential for becoming a commercially accepted part of this nation’s energy infrastructure. Biodiesel exhaust emission has been extensively characterized under field and laboratory conditions. Regarding research into any association of biodiesel exhaust exposure and human health end points, there are only a few cytotoxicity and mutagenicity studies. Investigation into an inflammatory and fibrotic response in vivo or induction of processes that are good biomarkers of these responses in vitro (e.g., cytokine production changes, comprehensive genomic analyses) has not been initiated. Similarly, any interaction of biodiesel exhaust emissions with the atopic state of an individual requires study.

An immediate need for any research focused on biodiesel exhaust and human health is production and collection of sufficient quantities of exhaust material to be shared by researchers. There are investigators who have isolated various extracts of biodiesel exhaust. These emission extracts have used widely divergent engines, conditions of running, fuels, fuel additives, and after treatments. Frequently, they are generated in quantities of milligrams or less. Under these circumstances, there are limits to both the end points that can be examined and the reproducibility of studies. Furthermore, it is unclear how applicable the results of any single study would be to the field.

Particles from both combustion and non-combustion processes are associated with an oxidative stress. After exposure to oxidant generation by numerous particles, a cascade of reactions follows in numerous, disparate cell types. This response includes activation of cell signaling, transcription factor activation, and release of proinflammatory mediators. The result is an acute inflammation both in the lower respiratory tract and systemically. This series of reactions may also be evident in response to biodiesel exhaust. This is testable using a myriad of in vitro and in vivo (animal and human) exposure methodologies. The soluble organic fraction present in petroleum diesel exhaust particles has been associated with both the generation of an oxidative stress and the magnitude of the cytokine response (Bayram et al. 1998; Boland et al. 1999; Bonvallot et al. 2001, 2002; Casillas et al. 1999; Kawasaki et al. 2001). The greater fraction of soluble organic fraction in biodiesel exhaust particles could affect both oxidative stress and the magnitude of the biologic response after exposure to biodiesel exhaust (Graboski and McCormick 1998).

It is our opinion that biodiesel requires greater due diligence than it has received to date in the United States. In widespread employment of biodiesel as an alternative fuel, there would be several additional issues pertinent to human health:

  • In the United States, biodiesel is sold as a blend with petroleum diesel [as either B2 (2% biodiesel) or B20 (20%)] and is considered an oxygenate. Such employment is likely to affect the quantity and the composition of emissions and potential biologic effects of the exhaust (Graboski and McCormick 1998). Eventually, research into potential consequences of biodiesel exhaust exposure on human health will have to consider blends.
  • Additives to biodiesel fuel are numerous and may affect human health. No emissions data are yet available for biodiesel combined with the additives required for practical application of biodiesel fuel use on a national level. These include cetane improvers, smoke suppressors, flow enhancers, cloud-point depressors, wax antisettling additives, and detergents to reduce injector nozzle fouling, antioxidants for unsaturated oils, and control of microbial growth. Some of these additives include metals. Ideally, their participation in the biologic effects of exposure to biodiesel exhaust should be tested.
  • Disparate levels of aldehydes in biodiesel fuel and its exhaust emissions may be associated with varying impacts on indices of human health. Low-quality biodiesel, which does not meet high production standards, will emit greater quantities of aldehydes because of poor post-transesterification refining. Studies also demonstrate that emissions from RME may have elevated concentrations of aldehydes relative to those from soybean methyl ester. It is unclear whether this might affect human health (Krahl et al. 2001).
  • Implementation of new petroleum diesel engine combustion and after-treatment technologies, designed to decrease specific exhaust components such as particulate matter and nitrogen oxides, will require re-evaluation of the emissions from biodiesel exhaust. The decrease in specific components is being driven partly by integration of new regulations and standards for on-road heavy-duty diesel engines and off-road regulations stretching out to 2016. Similar legislation regarding stricter emission standards from on-road heavy-duty diesel engines are being implemented in the European Union. However, it is not clear whether decreased emission rates of some targeted components (e.g., nitrogen oxides) decrease all health-related end points. In one report, a new diesel particulate trap technology can increase emissions of some toxic components (Ullman et al. 2003).
  • The use of pesticides on plants with subsequent contamination of feedstocks could possibly affect specific end points of human health and requires further investigation (Van Gerpen et al. 2004).

Currently there is a strong desire and need for alternative fuels in this country. Employment of biodiesel fuel is favorably viewed, and there are suggestions that its exhaust emissions are less likely to present any risk to human health relative to petroleum diesel emissions (Mauderly 1997). However, the speculative nature of a reduction in health effects based on chemical composition of biodiesel exhaust needs to be followed up with investigations using newer biologic approaches gained from years of diesel research. Studies into health effects of exposure to biodiesel exhaust should be initiated.

Environ Health Perspect. 2007 April; 115(4): 496–499.

Published online 2007 January 3. doi: 10.1289/ehp.9631.

Copyright This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.

Author - Armitage: 2007

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