Environmental Engineering Reference
In-Depth Information
investments in economies of scale, fuel conservation measures, or emissions control mea-
sures. If so, one indication would be di
erent rates of change for installed power on ships
providing goods movement compared to changes in cargo volume. In other words, if a
ff
eet
of ships can carry more cargo without a proportional increase in installed power, then it
must be adopting improved technologies (e.g. hull forms, engine combustion systems, plant
e
fl
ciency designs) or innovating its cargo operations (e.g. payload utilization).
In fact, the opposite trend is observed over the past 20 to 30 years, where
eet installed
power has grown at rates faster than global trade growth. Observed trends in average
installed power reveal a compound annual growth rate (CAGR) for installed power since
1985 is ~10.7% per year, more than twice the rate of world seaborne trade growth, driven
by increases in containership power, which grew at more than 16% CAGR over these two
decades. Rephrasing, ocean shipping may have become more energy intensive, not more
energy conserving. This seemingly counter-intuitive observation is typical of other trans-
portation modes, particularly on-road freight and passenger vehicles, and readily explain-
able in terms of trade globalization and containerization of international trade.
Globalization produced longer shipping routes, and containerization served just-in-time
(or at least on-time) liner schedules;
fl
both of
these drivers motivated economic
justi
cation for larger and faster ships which require greater power to perform their
service. Introduction of the fastest, largest ships
fi
rst occurred on the most valuable trade
routes (e.g. serving North America and Europe) where economics most justi
fi
ed the
higher-performing freight services. Increasingly over the past two decades, ships serving
all routes became faster and larger through intentional expansion and aging
fi
fl
eet transi-
tion from prime routes to secondary markets.
Even assuming that e
ciency improvements from economies of scale reduce energy
intensity and emissions rather than being directed to larger and faster ships (e.g. container
ships), compounding increases in trade volumes outstrip energy conservation e
ff
orts
unless technological or operational breakthroughs in goods movement emerge.
However, technological change might o
ff
set this trend, if
fl
eets can achieve greater
e
ciencies while increasing installed power (Wartsila NSD, 1998; Harrington, 1992;
Heywood, 1998). In other words, if fuel economy (energy input) is not directly propor-
tional over time to energy output (proportional to rated power), then improved propul-
sion technologies can explain the decoupling of increased power and fuel use. Adjusting
power-based trends for a number of factors, including
eet modernization and shipping
cycles, we estimate a world growth trend ranging between 3.8% and 4.5% CAGR.
Coincidentally, averaging bounding extrapolations yields between 3.8% and 4.5% CAGR
growth in installed power, nearly the same 4.1% CAGR as observed for past world
seaborne trade. In other words, this explains and con
fl
rms the use of seaborne trade
growth to project ship fuel use and emissions, as other studies have done. Consistent with
the market-forecast principles re
fi
ected in the IMO study, and given the strong relation-
ship observed between cargo moved (work done) and maritime emissions (fuel energy
used), we adopt for our forecasts the world average growth rate of 4.1%.
fl
Mitigation alternatives for shipping
Reduction of traditional air pollutants has received greater attention. Air emissions
technologies are generally adapted or marinized from similar engines in other indus-
tries (Wartsila NSD, 1998; Alexandersson et al., 1993; Corbett and Fischbeck, 2001;
