Biomass Yield

The yield is one of the most important ecological parameters, since all impacts on the environment have been related to it in order to characterise the energetic and "ecological" efficiency of an energy crop species (Scholz et al. 2006). The yields of the main products of conventional species such as cereals, oil and tuber crops are well known, whereas the yields of the whole plants are mostly not available in

Table 5.2 Relevant parameters indicating potential impacts on the environment caused by energy crop cultivation

Impact on environment

Parameter

Exhaustion of energy resources

Exhaustion of other limited resources

Anthropogenic greenhouse effect

Acidification

Eutrophication

Photosmog

Stratospheric degradation of ozone Human and ecological toxicity

Soil compaction Soil erosion Change in soil quality Change in water quality

Nutrient leaching to groundwater and surface water Change in biodiversity

Change in land use

Noise and odour Fire risk

Consumption of crude oil, natural gas, coal, uranium etc. Consumption of fertilisers, water (transpiration coefficient) etc. CO2 equivalents (CO2, CH4, N2O, VOCs, etc.) SO2 equivalents (NOx, NH3, HCl, HF, H2S, etc.) PO2 equivalents (NO^ NH3, NH4+, PO43- NO3-) C2H4 equivalents or NOx corrected equivalent. (CH4, NMHC, NO , ...) '

Diverse selected individual substances, e.g. pesticides, heavy metals and particulates (PM10 equivalent) Soil morphology and structure Loss of topsoil

Organic matter content; carbon content Critical values for drinking water (e.g. nitrate, pesticides)

Volume and choice of fertilisers; rate, timing, methods of application; runoff or leaching potential Measures of impacts on flora and fauna, e.g.

compatibility with native biomass, alteration of production and growth period and geographic distribution of populations and alterations in reproduction cycles of species Landscape diversity (e.g. crop diversity, farmland diversity)

Location of site (e.g. proximity to ecologically important areas) Scale of plantation (e.g. acreage) Diverse measures

Temperature, rainfall, wind, moisture, drought etc.

agricultural statistics and have to be calculated by means of the grain-straw or similar ratios. This may result in some errors because these ratios depend on various influencing factors and range over a wide span. Nevertheless, the method will do for a viable yield calculation (Table 5.3).

The yields of non-conventional crops such as Miscanthus sinensis, poplar and willow are little known. With the exception of willows in Sweden, these "new" energy crop species are mostly cultivated on small plots and are often at the research stage. Consequently, these yield data have to be examined critically. The published yields of M. sinensis, for instance, range between 8 and 22 tDM ha-1 year-1 and were mainly measured under special conditions (Fruhwirth et al. 2006; Scholz et al. 2007; Stolzenburg 2008). The denoted average yields of poplar and willow are a result of an expert census in Germany (KTBL 2006).

Table 5.3 Mean biomass yield, moisture content and heating value of appropriated energy crop species in Germany according to Schmitz (2003), BMELV (2006), KTBL (2006), Fr├╝hwirth et al. (2006), Rosillo-Calle et al. (2007), BMELV (2007a) and own data

Product

Yield

Moisturea

NHVb

Use

Species

-

(tDM ha-1 y-1)

(%)

(MJ kgDM-1)

Oil use

Rape

Seeds

3.0c

12

26.5

Sunflower

Seeds

2.2

12

-

Sugar/Starch use

Wheat

Grain

6. 4c

14

17.0

Winter rye

Grain

4.6c

14

17.1

Winter triticale

Grain

4.9c

14

16.9

Maize

Grain

7.6c

14

17.0

Potato

Tuber

8.9c

78

14.3

Sugar beet

Tuber

13.5

77

-

Ligno-cellulose

Wheat

Whole crop

14.0

16 or 65

17.1

use

Winter rye

Whole crop

9.8

16 or 65

17.7

Winter triticale

Whole crop

10.5

16 or 65

17.0

Maize

Whole crop

17.5

65

17.9

Perennial rye

Whole crop

8.5

16 or 65

17.7

Grass

Whole crop

9.0

16 or 65

16.5

Miscanthus

Whole crop

15.0d

16 or 65

17.6

Poplar

Whole crop

10.0d

54

18.4

Willow

Whole crop

7.0d

50

18.3

aMean moisture content of harvested products, in the case of whole haulm-type crops in the form of dry bales or chips (16%) or in the form of silage (65%)

bNet heating value (NHV) of absolutely dry material cMean long-term yield (2000-2005)

dNo statistically safe data

However, the statistical distribution of the poplar yield is very wide and ranges between <1.0 and >25 tDM ha-1 year-1 in Europe (Fig. 5.3). Nevertheless, the distribution of the poplar yields shows that some of these "new" energy crop species may have great potential if the right varieties are chosen for the right sites.

Organic Gardeners Composting

Organic Gardeners Composting

Have you always wanted to grow your own vegetables but didn't know what to do? Here are the best tips on how to become a true and envied organic gardner.

Get My Free Ebook


Post a comment