Carbon Emissions Pinch Analysis for emissions reductions in the New Zealand transport sector through to 2050
Introduction
Replacement of traditional oil and natural gas based transport fuels with alternatives that are both technically and economically viable and environmentally, socially and politically sustainable is a significant global issue. As transport energy demand rises, especially in developing countries, and as oil and gas reserves become increasingly difficult to find and exploit, energy companies and nations will be driven to convert unconventional energy resources, like tar sands, shale oil, agricultural crops and silviculture forests, into replacement fuels. Increased motivation to address the transports' fuel challenge is derived from the need to lower environmentally harmful emissions, such as carbon and the like emissions, and to reduce air pollution in many of the world's major cities. However converting unconventional energy resources into transport fuels, even after considerable research effort, remains a technical challenge and struggles to economically compete with oil-derived liquid fuels.
Careful energy sector planning using engineering analysis tools, such as CEPA (Carbon Emissions Pinch Analysis) [1] and EROI (Energy Return on Investment) analysis [2], is therefore needed to ensure that the inevitable transition to a low fossil fuel transport energy sector occurs in a way that minimises the increase in cost and energy expended from the economy to meet the desired demand within the nation's carbon emissions targets. EROI is essentially the ratio of the amount of useful energy produced for society to the amount of energy that has to be expended to obtain the useful energy in the first place. Effective production of energy with high EROI values is crucial to economic growth, industrial manufacturing, employment and the general economic well-being of citizens [3]. CEPA, on the other hand, quantifies the environmental impact in terms of emissions of using energy. CEPA is a graphical method for showing how much carbon emissions are contributed from each part of an energy sector (e.g. electricity, transport) and exploring possible pathways for modifying the energy system to meet fixed emissions targets.
NZ (New Zealand) is well endowed with natural energy resources. Renewable resources such as hydro (58%), geothermal (13%), wind (4%) and biomass (<1%) accounted for 77% of electricity generation in 2011 [2]. Coal, natural gas and biomass are used for process heat and the remaining power generation demand. Imported crude oil accounts for 33.8% of NZ's primary energy needs and 99.8% of NZ's transport fuel needs [4]. NZ has a current population of 4.4 million that is anticipated to reach 5.8 million about 2050 [5]. There is strong political will within NZ for continued growth in the renewable generation sector as a strategy for reducing NZ greenhouse gas (GHG) emissions. Numerous studies have been commissioned by the NZ government into alternate transport fuel options for NZ in the biofuels areas [6].
There are also many other studies that are specific to other countries that are in a similar energy and resource position as NZ that may be considered when exploring solutions for NZ. For example, Mathiesen et al. [7] conclude that Denmark should use their abundant renewable electricity generation potential to directly power as much of the future transport fleet as possible. Other transport operations such as aeroplanes and ships that cannot be electrified are anticipated to use liquid fuels from biomass. As a result, they are exploring ways to increase the carbon yield of liquid fuels from biomass through the direct or indirect integration of renewable electricity in the conversion process. These ideas may have merit for countries that have the natural resources to produce large quantities of renewable electricity at reasonably high EROI ratios. Maintaining high EROI levels for transport energy will help minimise the economic and environmental effects of transitioning from fossil fuels to other energy alternatives.
The aim of this paper is to apply a modified CEPA method to explore how NZ can meet its future transport demand in 2050 while reducing the associated carbon emissions to 1990 levels. Various methods for reducing emissions are investigated including production of biofuels, electrification of the transport fleet using renewable resources, and increases in combustion engine efficiency through hybrid systems. For example, we are attempting to define such items as how much biofuels NZ needs to produce, not how much biofuels NZ can produce. There will continue to be technical and economic challenges facing the quantum of biofuels NZ requires by 2050 to help achieve 1990 levels of emissions. As a result, this paper extends the CEPA for analysis of transport sectors where the transport demand can be divided into distinct classes. CEPA has been chiefly applied to electricity sectors in NZ [8] and Ireland [9] and extended to include carbon capture and storage (CCS) [10].
Section snippets
A modified Carbon Emissions Pinch Analysis framework for transport sectors
CEPA was first developed by Tan, Foo, and co-workers [1], and is based on the application of traditional Pinch Analysis techniques beyond Total Site Analysis for large industrial sites to broader macro-scale applications such as regional and national electricity generation sectors [9]. Sectorial and regional studies have been conducted for power systems emissions constraint planning [11] with CCS [10] including retrofitting [12] and for multi-period scenarios [13] and variable CO2 sources and CO
Transport efficiencies and fuel emissions factors
There are a wide variety of transport modes (e.g. marine, air, road, and rail) and many classes of vehicles or vessels within these modes. For example, within the road transport mode there are light trucks, heavy trucks, and light commercial vehicles. Within these classes, there are further subclasses of specific vehicle or vessel makes and models made to common specification and/or performance.
At the vehicle class level, transport fuel use, emissions and useful transport output can be
New Zealand transport sector fuel and emissions growth projections
The NZ transport sector has experienced significant growth in fuel demand from 1974 to 2008 as illustrated in Fig. 3. Petrol and diesel fuels dominate the growth in fuel use, followed by aviation fuels. Fuel oil declined in the 1980s and again increased in the 1990s. Responses to global recessions, oil price hikes and/or periods of economic restructuring are also evident in the fuel use data. As global oil prices rose in the late 1970s, economies like NZ were forced to spend more on foreign
Carbon Emissions Pinch Analysis for the New Zealand transport sector in 2012
Using the CEPA composite curve method the freight and passenger transport demands in NZ for the year 2012 are illustrated in Fig. 6. The fuel supply composite curve has not been included in Fig. 6 because it cannot clearly be distinguished from the demand curve, which is due to all current transport fuels being derived from crude oil with very similar EFs (Emissions Factor) within each vehicle class. Fig. 6 shows passenger transport contributes 12% of the useful transport output but is
Conclusion
Freight and passenger transport demand in New Zealand is anticipated to increase by 30% from 2012 to 2050 due to population growth. An important element of reducing carbon emissions attributed to transport in New Zealand is electrification of all rail and partial electrification of light passenger vehicles through plug-in hybrid and electric vehicle technologies to the degree of 5.4 TWhe, which replaces the equivalent of 49 PJ of conventional liquid fuels. New Zealand's electricity is supplied
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