In the past, environmental performance calculations in order to determine the environmental impact of transport used to focus on the negative impact of emissions on health and nature. These emissions have gradually come under regulatory legislation and are thereby being gradually reduced through more stringent legislation on cleaner fuels and combustion engines. With legislation and technical solutions reducing these emissions in combination with a growing concern on climate change, the performance calculations are increasingly focused on the emissions of green house gases, GHG. The measurability of different environmental aspects varies, hence performance indicators seldom reflect all the negative effects occurring from industrial activities.
For the transport sector, other relevant environmental aspects (negative external effects) would be noise, land use, impact on biodiversity etc. Due to problems to measure and establish common values for their impact, these aspects and emissions are generally included through estimations on their external costs. Using external costs for assessing environmental performance will however not be part of this article for evaluating environmental performance of transport services.
In addition to the increased climate change focus there is a strong focus on how the transport logistics industry on a global basis is to 96% dependent on fossil fuels. The issue is strongly linked to the expected decline of oil production, peak oil. Reduced oil production capacity will most likely lead to an increase of transport fuels price and thereby an increased demand of alternative fuels. Considering the critical high dependency on fossil fuels and the corresponding emissions of green house gases there is a need to measure and monitor the transport sectors use of fossil fuels from a life cycle perspective.
As today´s transport logistics system is based on transport techniques that gradually are being updated with cleaner techniques corresponding to economic resources, it is still relevant to include all use of resources as well as the emissions affecting local health, regional biotopes and the global climate system.
The conclusion is that environmental performance assessment should still include all emissions and use of transport fuels. Due to uncertain values on costs for other external effects these aspects are excluded in this model.
Performance indicators
An environmental assessment of a carried out transport service estimates the environmental performance based on a number of assumptions, models and activity data. The performance outcome can be described in absolute or relative terms. The absolute measurement indicates actual impact on the environment from a transport activity while relative data describes the environmental efficiency of the transport activity. For goods transport services, the activity could be one single transport link or a transport chain from shipper to consignee. The absolute performance indicators are commonly expressed as amount of used resources such as [MJ, kWh, litre, kg] for the activity and corresponding amount of emissions from the activity. For transport services this is air borne emissions from combustion, but also leakage and wear [kg, ton]. Leakage occurs unintentionally but unfortunately also as deliberate actions. The relative performance indicators are based on the absolute indicator in relation to accomplished benefit, expressed as transport work [g/tonkm], time unit [litre/h] or economic turnover or result [kg/monetary unit, EUR etc.].
Geographical considerations
Another much debated aspect of environmental performance assessment is how the environmental effect of emissions may vary in relation to geography, altitude or time. The negative environmental impact from acid rain is, for example, substantially lower in regions with a large proportion of lime stone in the ground in comparison with regions with low amount of lime stone. Leakage of oil reaching the shore during the time of birds breeding period being in the polluted area gives of course more damage compared to times when the birds are at sea. Some high altitude emissions have according to certain scientist’s additional effects adding to the green house effect. Overall, the inclusion of effects to the assessment of environmental performance is relevant, but it also increases the complexity of the analysis. Effects bring in several new scientific areas into the analysis. From a transport logistics service provider or buyer of that service, the most relevant scope is however to minimize the use of resources and reduce emissions.
Assumptions
An environmental performance assessment can also describe future expected environmental performance as forecasts or scenarios. Describing future performance includes assumptions on scientific and organizational progress. In this article we only describe performance assessment of already carried out services based on known technical and organizational calculation conditions. Calculation methodology for the forecasts is essentially the same, but forecasts uncertainties in terms of probabilities on the input data must be monitored in the final outcome of the relevant assessment results. Another aspect of forecasting is the impact on neighbouring systems. Suppose a scenario with the transition from truck to electrified rail. This may adversely affect the remaining truck transportation systems that lose balanced freight flows and increase that transport system’s relative environmental impact. Increased rail transport requires additional electrical power where an increase in demand for electricity generation can at worst have to be supportive of coal plants. Overall, the penalty can be expected that the environmental benefits will be less than at first envisaged. Marginal effects can include both negative and positive environmental impacts.
Calculation methodology development
The Network for transport and environment, NTM are actively working within the field of standardisation of environmental performance assessment since 1993. Today NTM is also active in the development of a European standard on transports energy use and emissions of green house gases. NTM is furthermore developing product category rules (PCR) for transport services from which environmental product declaration (EPD) can be established for specific transport solutions. PCR/EPD includes all modes of transport and includes energy, green house gases and general regulated emissions. The PCR structure is based on the ISO 14 025. For more information on the NTM work, www.ntmcalc.org.
System boundaries
Typically, when calculating the environmental impact of a carried out transport service is to include the resource consumption of inputs, primarily fuel and electricity consumption and corresponding emissions generated by the transport activities. The extent of resource use and emission activity is determined by the system limits set for environmental assessment. According to various studies, supportive and indirect activities of transport service can constitute a significant part of overall resource consumption and transport emissions . With a system boundary that includes support and indirect activities more environmental factors and resource use are added. This will generally make the estimation more extensive and complex. Below is a comprehensive breakdown of the various relevant systems boundaries, excluding each subsystem´s upstream and downstream system.
• System boundary A, including traffic and transport related activities regarding engine operation for the propulsion and equipment for climate control of goods, and losses in fuel tanks and batteries. This includes the traffic-related terminal handling, i.e. when goods do not leave their vehicle/vessel.
• System boundary B, which includes the supply of energy from energy source to the tank, battery and electric motor (trains). This system boundary is the system together with system boundary A that is the minimum required for performance comparisons between different modes of transport.
• System boundary C, traffic infrastructure operation and maintenance
• System boundary D, vehicle, vessel, load units production The above system boundaries should not be seen as mutually inclusive or exclusive, but rather as a sub-sample that can be added or subtracted from, depending on the environmental assessment. Altogether, there are some important rules which must be fulfilled for the choice of system boundary:
1. When assessing environmental performance, the results should monitor the included system boundaries
2. Comparison of different transport solutions must be done with comparable and relevant system boundaries
3. When comparing the same transport system over time, this must be done by using the same system boundary.
Comparing different propulsion and energy supply systems
For comparison of different transport systems, based on different propulsion systems and energy supply systems it must be done with comparable system boundaries. The following aspects need to be considered:
1. Electric motor: Electric power for vehicle/vessel propulsion directly linked to electric distribution grid through pantograph. Electricity is generated at optimum production plant (production costs and market situation) simultaneously with consumption.
2. Plug-in electric motor: Electric power for vehicle/vessel propulsion through accumulators (batteries) is generated at demand or at optimum production plant and time (production costs and market situation).
3. Combustion engines: Transport fuels for vehicle/vessel propulsion with combustion engine is being produced at demand or at optimum plant and time related to production costs and market demand.
In all three cases of traffic operation, the transport fuels for vehicle/vessel propulsion have been preceded by upstream processes that enable the delivery of electricity or fuel. This means that the whole upstream processes for all systems must be included for a fair comparison. An obvious example of the differences in outcome in environmental calculations with different system boundaries is how tail pipe fossil fuel carbon oxides from diesel combustion in vehicles or vessels is lower in comparison of another calculation that also includes refining and distribution of fuelsii.
The transport production system
An essential part of a transport chain is the terminals (ports, airports, etc), which are used in order to obtain an efficient transport system through increased resource utilization. Overall, transport operations are basically carried out by the same logic regardless of traffic mode where small flows of goods are handled with smaller vehicles and vessels while the freight flows in the long haul are handled by large vehicles and vessels. The goal is always to achieve economic and energy scale advantages. Cargo terminals have different characteristics depending on the mode of transport. The total resource use and emissions of terminals and warehouses in the whole transport chain is usually small in relation to transport. For a completely accurate and comprehensive assessment of environmental effects, terminals handling should be included with the same system boundary as for the corresponding transport service. If terminal handling is excluded on the grounds that they constitute a negligible portion (cut-off rules) of the whole transport chain this must be clearly stated in the reported results.
Allocation of environmental burden
One area of ongoing discussion is how large proportion a shipment should include of total traffic resource use and emissions. The general description of this is that all resource use and emissions of vehicles and vessels must be allocated to the transported goods (and passengers in a combined shipment). Allocation should be done by the delimiting factor of that specific transport system, i.e. weight, volume etc. Allocation must also include resources and emissions for the positioning of empty laden trips. Relevant principles for allocation of empty trips differ between various transport systems. The allocation is obviously even more complex with transport that includes both goods and passengers. Different keys for allocation can be used but should be based on what actually drives the environmental impact of the analyzed transport mode. It is furthermore important to allocate support functions correctly. Additional equipment required for cargo and passengers should be allocated on the user of this equipment. In aviation, where a significant proportion of freight is carried in passenger aircraft (belly freight), galley, flight attendants etc should be allocated as passengers. The same applies to any load carriers (pallets) that may be required for air transport of cargo. This tare weight should be allocated to the cargo. Combined transport service of freight and passengers occur on a regular basis within air and ferry transport. Within road and rail transport this is not equally frequent. A very practical and important implication of allocation is that increasing the load factor of freight and passengers leads to reduced relative emissions. Load factor is a well known crucial factor for good performance. As seen in the figure below it presents how high resource utilization leads to more goods that can share the negative environmental impact. Since the total fuel consumption and emissions do not increase equally much with increased utilization, the relative emissions are reduced by increased utilization.
i Environmental assessment of passenger transportation should include infrastructure and supply chains. Mikhail V Chester & Arphad Horvath, 2009, University of California. ii NTM Fuels