Biofuel potential of Rushes

January 12, 2018 | Author: Anonymous | Category: Science, Biology, Ecology
Share Embed Donate


Short Description

Download Biofuel potential of Rushes...

Description

Biofuel potential of Rushes

Scope • Potential of rush as a biofuel • Determine calorific value • Compare with available alternatives

Juncus effusus • Juncus family - Approx. 300 spp worldwide • J effusus habitats are diverse – moist areas at forest margins, – wet grasslands, – wetland margins – lake shores – river banks – wet meadows – Some bog

Soft Rush • Moderate amount of research on Juncus spp in Ireland • Slightly surprising given label as agricultural weed • Might suggest that issues concerning soft rushes are minimal or have been solved

In Ireland • Broad distribution in Ireland • In many areas, with poorer soils, some fields almost completely covered • Some work to reclaim peat soils for agricultural use in Mayo in 2001 – but soft rush invaded and became dominant

Biology • Hab prefs previously covered • Rhizome permits vegetative growth producing new shoots and also reproduces by flowering

www.irishwildflowers.ie

Biology • Rhizome grows at about 2cm per year • Can send adventitious roots up to 50cm below surface, commonly 20cm • Growth of roots and shoots accelerates from March onwards – flowers June/July/August

Growth

Growth reaches a maximum in the summer and is generally positively correlated with seasonal climatic factors, and negatively correlated with standing - dead biomass parameters

Growth • Produces very high numbers of seeds estimated at 4 milion per square metre • But seeds represent tiny fraction of biomass produced annually (0.27%) • Soil seedbank remains viable and provides for events such as flooding

‘Control’ • Undesirable aspects of soft rush growth not a recent problem. • Classified as a weed as it is unpalatable to stock and low feed value It is well known as an agricultural • Soft rush is quite resilient, not normally eaten by stock, but they will at high densities

• Soft rush resistant to grazing pressure, trampling and annual cutting

Control • Hydrologic conditions that favour the development of rush stands will not change with control methods such as: – Cutting – Herbicides – Grazing

• Common to drain and cut or cut and spray

Effects of cutting • Research in 1939 - two cuts in two consecutive years produced an 80% reduction in shoot numbers • This work also stated that it was important to have first cut in July – before and after was less effective at control

• Work in 1936 suggested that rushes seemed to be most susceptible to weakening if cut shortly after mid - summer. • Others noted that some rush species do not flourish at sites where hay is cut annually fields cut for hay year after year. • Trials in 1964 found that mowing repeatedly 4–6 times per year was required to control the rushes but would not eliminate them.

Effects of cutting • 1995 work suggested that cutting to half their height had no effect • Cutting to ground level twice a year over two years effective at controlling them • Most control methods in use in Ireland involve herbicides in combination with cutting or drainage – depending on land use

Energy Content • Determined moisture content – 5 size classes of rush

20 – 30 cm 30 – 40 cm 40 – 50 cm 50 – 60 cm >60cm

Moisture content Length class

Number of rushes

Mean length

Wet mass(g)

Dry Mass

% Moisture

20-30cm

12

25.46

4.35

3.01

30.72

30-40cm

16

33.93

10.73

7.48

30.32

40-50cm

34

45.1

28.89

20.23

29.99

50-60cm

23

53.26

26.79

18.83

29.72

60-70cm

15

64.1

21.67

14.79

31.75

Rushes had approx 30% moisture content when harvested

Moisture content • Also looked at some commercial products MACE wood briquettes approx NCF wood logs approx Turf Peat briquettes Kiln dried wood Miscanthus Strogs

25% 15% 16 - 35% 10% 9% 9 - 20% 12%

Energy content • Used bomb calorimeter • Calibrated with standard material • Determines energy content by ability to heat known mass of distilled water when substance is combusted in presence of oxygen

Energy Content Fuel

MJ/Kg

Coal

27.1 - 33

Straw Briquettes

16

Miscanthus

18

Turf

14-18

briquettes

17

>60cm rush

17

50-60cm rush

18.7

NCF wood logs

19

Mace wood briquettes

19

Summary to date • High moisture content but relatively easy to dry • Obviously don’t have to get moisture to zero • Very low ash content on combustion • Very low density when dry • Energy content comparable to currently available products • Perhaps consider them as an addition

Main source • Forest Ecosystem Research Group Report Number 69

View more...

Comments

Copyright � 2017 NANOPDF Inc.
SUPPORT NANOPDF