Environmental Engineering Reference
In-Depth Information
biomass production in the second rotation. Al Afas et al. (2008) summarized the biomass yields
over 3 rotations (11 years) from the above studies at Boom, Belgium. Biomass production varied
with clone and rotation. Biomass increased from year to year within a rotation, but declined with
number of rotations. The N × T hybrids were the “best” overall performing clones and were “best”
adapted to multiple coppice rotations.
Recent EU policy changes have had a major effect on efforts to find high yielding poplar biomass
systems. The goal is to double EU renewable energy use from 6 to 12% by 2010 (Klasnja et al.
2006). Therefore, there has been an increase in the poplar biomass production studies in Europe.
Sixto et al. (2006) reported 18 new experimental studies of poplars with very high density plantings
(i.e., 15,000-33,000 trees/ha) of many poplar clones. Their goal is to identify high biomass pro-
ducers while providing environmental benefits and rural employment. Scarascia-Mugnozza et al.
(2006) reported 5000 new ha of poplar plantations in northern Italy. New clones improve yields by
100%, yielding 18-24 mt/ha per year. The maximum yield was 20 mt/ha per year. The studies also
investigated the use of animal and urban wastewater for irrigating short rotation poplar plantations.
More recent results are even more favorable. New clones with N fertilization are producing an aver-
age of 23 mt/ha per year and have achieved up to 50 mt/ha per year (Paris et al. 2008). The Italian
Ministry of Agriculture has also recently financed new research on poplar biomass supply chains.
The goal is to use poplar biomass for feeding district heating plants. Early results confirm biomass
yields of 20-25 mt/ha per year planted at different spacings and rotations (Facciotto et al. 2008;
Nervo et al. 2008).
15.4.2.3 other countries
The largest poplar plantations in the world are in China. China has over 4.3 million ha of poplar
plantations and an additional 2.5 million ha of poplars used in agroforestry (FAO 2008). India also
has vast areas of poplars used for agroforestry (Puri and Nair 2004), and Turkey has over 138,000
ha of planted poplars; again, large areas are planted under agroforestry with poplars interplanted
with beans, corn and melons (Toplu 2008). There are large areas of poplars used for agroforestry
and silvo-pasture in New Zealand (FAO 2008), and in the 1960s there were plantations of poplar in
Australia and South Africa (Pryor and Willing 1965). There are also an increasing number of poplar
plantations in South America (Eaton 2008b).
Small farmers in China, India and Turkey have been using poplars for fuelwood since antiquity,
but until recently poplar plantations were used mostly for traditional wood products and not
bioenergy. Fang et al. (1999) reported 6 year results of short rotation poplars in China with annual
biomass increments of 17 mt/ha per year. Biomass yields differed considerably with planting den-
sity, clone and rotation length. In later reports, Fang et al. (2006, 2007) reported biomass yields of
14.6 mt/ha per year for three poplar clones at age 10. Das and Chatuverdi (2009) reviewed biomass
production of poplars in agroforestry systems in India and reported biomass yields of 5-10 mt/ha
per year. Dhanda and Kaur (2000) also reported on poplar biomass production in an agri-silviculture
system in Punjab, India. There is great potential in South America for growing poplars for biomass
production. Eaton (2008b) reported test yields of genetically improved poplars of 30 mt/ha per year
in Chile.
15.4.3 B
ioEnErgy
from
p
oplarS
Interest in biomass for energy accelerated after WW II (Young 1973). Wood energy plantations were
seen as a way of achieving energy independence. Szego and Kemp (1973) were early proponents of
the “energy forests” or fuel plantations. Up until that time, short rotation plantations were viewed as
a solution for maximizing fiber yield and taking the pressure off of native forests to help provide the
nation's pulpwood supply (Dawson 1976). Then, came the OPEC oil embargo in 1973. The embargo
changed the public and government attitude toward alternative energy sources, such as biomass.
Notably, Stephens (1976) gave the keynote address at an International Cottonwood Symposium
