Biofuels: Environmental Friend or Foe?

Presentation to 1st Year

Environmental Engineering Students

Deniz Karman

What are biofuels?

Why biofuels?

Why not biofuels?

Life-cycle analysis

Primary energy sources

• Coal• Oil• Natural gas• Hydro• Nuclear• Solar• Wind• Biomass

Energy carriers:• Electricity• Hydrogen

Energy conversion systems for transportation

• IC engines• Electric vehicles (EV)• IC-electric hybrids• Fuel cell vehicles (FCV)• FCV hybrids

}“Fossil”

fuels

Grain

Corn

SugarCane

Cellulosic Material

Ethanol C2H5OH

Biodiesel feedstocks:- Oilseeds

soybean, canola (rapeseed)- Waste oil - Animal sources

Biofuels

• Can we quantify the positive and negative impacts to make an overall assessment?

• Some easier than others, e.g.:

“CO2 emissions” vs “biodiversity”or,Socio-economic factors

• Case study: CO2 reductions – how much?

(Oxburgh 2008)

• Life cycle analysis

How are the CO2 emissions per unit energy in the previous chart calculated?

• The combustion of ethanol emits the same quantity of CO2 per unit energy regardless of the sources of the ethanol.

• If the C in the ethanol comes from biomass, it was captured from the atmosphere and does not represent a net emission

• The difference in the emissions results from the energy use during the cultivation and processing of the feedstock to obtain the ethanol

• Thus we cannot look at just the emissions during combustion and must do a life-cycle analysis to quantify the CO2 emissions

The phases in the life of a product

We can identify the energy requirements and environmental emissions associated with each phase.

Life-cycle analysis aims to quantify these.

Recycling avoids some

(but not all) of these energy requirements and emissions.

The life-cycle of a paper grocery bag.

Recycling paper avoids some (but not all) of these energy requirements and emissions.

Alternatively, plastic (polyethylene) grocery bags can be used.

To compare the two options we need to complete a life-cycle analysis for both products.

Life-cycle analysis for motor vehicles

Vehicle Cycle

FUEL CYCLE

Upstream operations:Feedstock and Fuel production, transportation, storage, and distribution

Vehicle operation: energy conversion and emissions from combustion

Pre-operation: Material production, component fabrication and vehicle assembly

FUEL

Post-operation: Vehicle disposal and recycling

New vehicles

Old vehiclesThere are energy requirements and pollutant emissions associated with each of these stages

Objective and quantitative evaluation of environmental performance for fuel/vehicle technologies

Figure 2 Comparison of the greenhouse gases emitted by biofuels in comparison to those emitted by fossil fuels (petrol and diesel, EURO3). The emissions are broken down into the individual process of the value chain.

How can we try to capture some of the other factors that are relevant for comparing the environmental performance of alternative fuels?

One example follows.

Figure 3 Comparison of aggregated environmental impact (method of ecological scarcity, UBP 06) of bio fuels in comparison with fossil fuels (petrol, diesel and natural gas). The environmental impact is broken down by individual processes of value chain.

The method of ecological scarcity (UBP 06). . . estimates the total environmental impact from the difference between emission values and the legal limits.

Conclusions

• Not all “biofuels” are the same in terms of their positive and negative effects.

• The motivation for and the effects of biofuels differ among different regions of the World

• Life cycle analysis is a MUST in assessing the environmental impacts of biofuels but may not give all the answers

• “apples” and “oranges” may need to be compared