Problem of deforestation in Portugal Valgreen Project

1. Composting of Acacia longifolia
and Acacia melanoxylon
invasive species

2. Acacia longifolia

3. Acacia melanoxylon

4. Acacia longifolia and Acacia
melanoxylon invasive species
Introduced in Portugal:
to mitigate dune erosion and loss of coastal landscapes
to fix biological nitrogen (N) for soil restoration
as ornamental plants
wood

5. Acacia longifolia and Acacia
melanoxylon invasive species
Fabaceae highly competitive
threat to local biodiversity
and natural habitats
significant fire risk

6. Acacia longifolia and Acacia
melanoxylon
new valorization approaches for these
shrubs are needed taking into account their
high availability and low cost.
Suggestion:
Composting to produce organic soil
amendments and horticultural
substrate components

7. Acacias have large recalcitrant
lignin, polyphenol and cellulose
contents that do not contribute to
raise composting temperature
enough to destroy acacia seeds.
(slow pathway)
However, acacia is also rich in N …

8. and when N is easily available the
slow-growing fungi that are able to
decompose lignin, such as the
basidiomycetes, are eliminated
from the decomposer community
because they are not capable to
compete with fast-growing
microbes.

9. Other conditions including
particle dimensions,
pile size and turning frequency,
affect heat loss or retention, and so,
final pile temperature.

10. Objectives
To analyse the physicochemical
characteristics during composting;
To model the breakdown of OM;
To find out if composting may reach
high enough temperatures for compost
sanitation and weed seed destruction.

11. Two big piles (100 m3) were set up
with grinded and screened Acacia
longifolia and Acacia melanoxylon
shrubs and were composted (231 days)
with different turning frequency …
Pile A: on day 28, 56, 84 and 147
Pile B: on day 28 and 147

12. Acacia harvest
The shrubs were harvested by basal cutting

13. Before

14. After

15. Transport

16. the branches and leaves were ground
with a high speed grinder
Grinder

17. Grinder
the branches and leaves were shredded
with a high speed grinder

18. Neuenhauser Super Screener Portable Star Screen
and screened

19. Particle size <10, <40, (>40 mm rejected)
The piles were built with particles < 4 cm

20. Composting piles
on a layer of pine bark with ± 30 cm

21. Turning with a forest crane and a
tractor front-end loader

22. Turning with a forest crane and a
tractor front-end loader

23. Temperature sensors and
seed packets

24. Viable seeds

25. Temperature probes
in the base, center and top of each pile
(approximately 0.5, 1.5 and 2.5 m high).

26. Composting piles after turning

27. Temperature – Piles A & B
0
25
50
75
100
0 60 120 180 240
Temperature(C)
Composting time (days)
Ta A center B center

28. Temperature – Pile A
0
25
50
75
100
0 60 120 180 240
Temperature(C)
Composting time (days)
Ta A top A center A down
The lowest temperature in
the bottom can be explained
by the evaporative cooling
effect of the incoming air

29. Temperature – Pile B
0
25
50
75
100
0 60 120 180 240
Temperature(C)
Composting time (days)
Ta B top B center B down

30. The temperature conditions satisfied
the compost sanitation requirements
specified by the U.S. Environmental
Protection Agency (USEPA, 1989).
significant reduction in pathogens
is achieved when temperature is
maintained above 55°C for ≥5 days.

31. Time-temperature conditions also
exceeded the more stringent criteria
for complete pathogen inactivation
proposed by Wu and Smith (1999)
equivalent to 55 °C for ≥15 days
as temperatures were kept between
65 ºC and 75 ºC for several months…

32. … indicating high total amount of
biodegradable OM in the composting
cells, and also the effects of pile size,
OBS: the heat generation is
proportional to volume and the heat
loss is proportional to surface area.

33. composting proceeded at optimum
MC for microorganism activity
40
50
60
70
80
0 30 60 90 120 150 180 210 240
Moisturecontent(%)
Composting time (days)
A
B
Pile
And contributed for long retention time of the
high temperatures inside the composting piles

34. Water evaporation was balanced by:
(i) winter and spring precipitation;
(ii) water produced during OM
degradation; and
(iii) mass reduction.

35. pH values increased early during the process as a
consequence of the degradation and
mineralization of organic acids and ammonia
production.
5
6
7
8
9
0 30 60 90 120 150 180 210 240
pH(H2O)
Composting time (days)
A
B
Pile

36. 5
6
7
8
9
0 30 60 90 120 150 180 210 240
pH(H2O)
Composting time (days)
A
B
Pile
These pH values do not limit the use of this compost
as soil amendment . The same is not true as
substrate component as pH for horticultural growing
media should be between 5 and 6.5

37. Final EC values of composts were well below the
maximum value of 3 dS m-1 recommended for
application to soil and is acceptable for nursery
production.
0,0
0,5
1,0
1,5
2,0
0 30 60 90 120 150 180 210 240
EC(dSm-1)
Composting time (days)
A
B
Pile

38. Dry matter loss was more than
50% of the initial DM.
0
200
400
600
800
0 30 60 90 120 150 180 210 240
DMlosses(gkg-1)
Composting time (days)
A
B
Pile

39. OM content decreased from 852 g kg-1
at the beginning of composting, to a
minimum of 637g kg-1 in final compost
500
600
700
800
900
1000
0 30 60 90 120 150 180 210 240
OMcontent(gkg-1DM)
Composting time (days)
A
B
Pile

40. N content increased from 9.5 g kg-1 at
the beginning of composting, to a
maximum of 12.3 g kg-1
4
6
8
10
12
14
0 30 60 90 120 150 180 210 240
Ncontent(gkg-1DM)
Composting time (days)
A
B
Pile

41. As would be expected, little NO3
--N accumulated
in composting piles during the thermophilic
phase because the bacteria responsible for
nitrification are inhibited by temperatures
greater than 40 °C
0
40
80
120
160
200
0 30 60 90 120 150 180 210 240
N-NO3
-(mgkg-1DM)
Composting time (days)
A
B
Pile

42. Low NO3
--N contents measured during the initial
stage of composting imply that the risk of N
leaching is minimal during this phase of the
process.
0
40
80
120
160
200
0 30 60 90 120 150 180 210 240
N-NO3
-(mgkg-1DM)
Composting time (days)
A
B
Pile

43. Rapid OM degradation (and N losses) followed
by slow degradation (and small N losses)
0
200
400
600
800
0 60 120 180 240
Losses(gkg−1DM)
Composting time (days)
OM NPile A
OMm = 300 (1-e-0.304t) + 340 (1-e-0.017t) r2 = 0.91***
Nm = 102 (1-e-0.168t) + 359 (1-e-0.051t) r2 = 0.85***

44. Rapid OM degradation (and N losses) followed
by slow degradation (and small N losses)
0
200
400
600
800
0 60 120 180 240
Losses(gkg−1DM)
Composting time (days)
OM NPile B
OMm = 359 (1-e-0.192t) + 423 (1-e-0.007t) r2 = 0.94***
Nm = 320 (1-e-0.247t) + 140 (1-e-0.017t) r2 = 0.82***

45. High temperature and high pH
conditions during the thermophilic
stage probably promoted intense
ammonia emission which would
explain high N losses.
Most of N losses occurred at the initial
phase of composting when OM
degradation, and ammonia
production, was at its most rapid.

46. The C/N ratio declined from initial values of
50±2.7 at the beginning of the process to 29-32
towards the end of composting.
20
30
40
50
60
0 30 60 90 120 150 180 210 240
C/Nratio
Composting time (days)
A
B
Pile

47. The C/N reduction was the result of a higher OM
mineralization compared to N volatilization
20
30
40
50
60
0 30 60 90 120 150 180 210 240
C/Nratio
Composting time (days)
A
B
Pile

48. CONCLUSIONS (1/4)
Grinded and screened acacia shrubs have
sufficient biodegradability and structure to allow
active composting with good air supply
thermophilic temperatures were attained soon
after pile construction and were above 65°C for
enough time to satisfy the more stringent
criteria for complete pathogen inactivation.

49. CONCLUSIONS (2/4)
Organic matter losses (640-690 g kg-1)
were increased compared to N losses
(≈ 460 g kg-1) and so C/N ratio
decreased from an initial value of 50 to
final values of ≈ 30.

50. CONCLUSIONS (3/4)
This study indicates that composting
acacia can produce organic
amendments with high OM content
and an EC well below the maximum
value recommended for application to
soil and for nursery production.

51. CONCLUSIONS (4/4)
However, a long period (> 231 days) of
composting is required to achieve full
compost maturation.
Further investigation will be carried out to
evaluate compost maturation and final
composts as components for horticultural
substrates.

52. Acacia composts characteristics to
replace peat moss in the formulation of
horticultural substrates (growing media)

53. Pile Day 147 Day 420
Mean ±*
SD Mean ±*
SD
Bulk density (g cm-3
) A 0.13±0.01 b 0.24±0.02 a
B 0.12±0.01 b 0.26±0.02 a
Real density (g cm-3
) A 1.67±0.03 c 1.78±0.07 b
B 1.74±0.05 bc 1.96±0.08 a
Total pore space (% v/v) A 92.0±0.8 a 86.5±1.5 b
B 92.9±0.5 a 86.6±1.5 b
Volume shrinkage (%) A 24.0±3.1 a 23.1±2.7 a
B 25.7±3.0 a 21.7±6.6 a
The bulk density was always below the maximum of
0.4 g cm-3 recommended for use as growing media for
ornamental potted plant production.
The real density of the composts, was within the
recommended range (1.4 to 2.0 g cm-3).
Abad et al. (2001)

54. Pile Day 147 Day 420
Mean ±*
SD Mean ±*
SD
Bulk density (g cm-3
) A 0.13±0.01 b 0.24±0.02 a
B 0.12±0.01 b 0.26±0.02 a
Real density (g cm-3
) A 1.67±0.03 c 1.78±0.07 b
B 1.74±0.05 bc 1.96±0.08 a
Total pore space (% v/v) A 92.0±0.8 a 86.5±1.5 b
B 92.9±0.5 a 86.6±1.5 b
Volume shrinkage (%) A 24.0±3.1 a 23.1±2.7 a
B 25.7±3.0 a 21.7±6.6 a
Total pore space (TPS) of final composts was above 85% of
the total volume of the substrate as recommended by
Verdonck and Gabriëls (1992).

55. Pile Day 147 Day 420
Mean ±*
SD Mean ±*
SD
Bulk density (g cm-3
) A 0.13±0.01 b 0.24±0.02 a
B 0.12±0.01 b 0.26±0.02 a
Real density (g cm-3
) A 1.67±0.03 c 1.78±0.07 b
B 1.74±0.05 bc 1.96±0.08 a
Total pore space (% v/v) A 92.0±0.8 a 86.5±1.5 b
B 92.9±0.5 a 86.6±1.5 b
Volume shrinkage (%) A 24.0±3.1 a 23.1±2.7 a
B 25.7±3.0 a 21.7±6.6 a
The volume shrinkage of Acacia composts (22 – 26%) was
below the upper limit value considered acceptable for
most substrates (Abad et al., 2001).
Total pore space (TPS) of final composts was above 85% of
the total volume of the substrate as recommended by
Verdonck and Gabriëls (1992).

56. The easily available water (EAW) of composts increased
with composting time and was above the minimum value
of 20% recommended by de Boot & Verdonck (1972).
0
20
40
60
80
100
A B A B
Day 147 Day 420
Volume(%)
AC
EAW
BC
LAW
DS
Composting Time
EAW
EAW

57. The buffering capacity also increased with composting
time and was also above the recommended limit of 4%
in final compost .
0
20
40
60
80
100
A B A B
Day 147 Day 420
Volume(%)
AC
EAW
BC
LAW
DS
Composting Time
BC
BC

58. The total water-holding capacity (TWHC) increased with
composting time. Final compost was above the minimum
recommended values of 60 % (Abad et al., 2001) and 55%
(Noguera et al., 2003)
0
20
40
60
80
100
A B A B
Day 147 Day 420
Volume(%)
AC
EAW
BC
LAW
DS
Composting Time
EAW
EAW
BC
BC
LAW
LAW

59. Air capacity decreased with composting time due
particle size reduction.
0
20
40
60
80
100
A B A B
Day 147 Day 420
Volume(%)
AC
EAW
BC
LAW
DS
Composting Time
AC
AC

60. Pile Day 147 Day 420
Mean ±*
SD Mean ±*
SD
pH A 7.2±0.1 b 7.3±0.1 b
B 7.3±0.2 b 7.7±0.1 a
EC (dS m-1
) A 0.7±0.1 b 1.1±0.1 a
B 0.8±0.1 b 1.4±0.1 a
CEC (cmol+ kg-1
MO) A 88±29 b 129±9 a
B 102±8 b 131±38 a
MO (g kg-1
) A 715±11 a 583±24 c
B 657±30 b 586±26 c
C/N A 36±1.8 a 26±1.3 b.c
B 29±3.7 b 23±3.1 c
The pH was alkaline (7.2 – 7.7) and above pH values set by
Abad et al. (2001) for commercial substrates (5,3-6.5) or
established as optimal values ​​(5.2-7.0) for the growth of
most greenhouse crops (Herrera et al., 2008).

61. Pile Day 147 Day 420
Mean ±*
SD Mean ±*
SD
pH A 7.2±0.1 b 7.3±0.1 b
B 7.3±0.2 b 7.7±0.1 a
EC (dS m-1
) A 0.7±0.1 b 1.1±0.1 a
B 0.8±0.1 b 1.4±0.1 a
CEC (cmol+ kg-1
MO) A 88±29 b 129±9 a
B 102±8 b 131±38 a
MO (g kg-1
) A 715±11 a 583±24 c
B 657±30 b 586±26 c
C/N A 36±1.8 a 26±1.3 b.c
B 29±3.7 b 23±3.1 c
The EC was above the maximum recommended value set
by Abad et al. (2001) of 0.5 dS m-1

62. Pile Day 147 Day 420
Mean ±*
SD Mean ±*
SD
pH A 7.2±0.1 b 7.3±0.1 b
B 7.3±0.2 b 7.7±0.1 a
EC (dS m-1
) A 0.7±0.1 b 1.1±0.1 a
B 0.8±0.1 b 1.4±0.1 a
CEC (cmol+ kg-1
MO) A 88±29 b 129±9 a
B 102±8 b 131±38 a
MO (g kg-1
) A 715±11 a 583±24 c
B 657±30 b 586±26 c
C/N A 36±1.8 a 26±1.3 b.c
B 29±3.7 b 23±3.1 c
Cation exchange capacity increased with composting time
C/N ratio decreased with composting time

63. The ratio NO3
--N/ NO4
+-N was <1 at the
end of the composting period suggesting
that the composts were matured (Larney
and Hao, 2007)

64. Experiments with
replacement of pine bark compost
by Acacia compost
in the composition of a commercial
substrate

65. Lettuce growth increased for the highest rate of
compost application, which may be related to the
lower C/N ratio and increased N availability in
Acacia composts, compared to the pine bark
compost

66. The replacement of pine bark compost by Acacia
compost in the commercial substrate did not
negatively affect lettuce germination, emergence
or growth; neither did it for cabbage growth.

67. Conclusions
1. Ground acacia biomass have sufficient
biodegradability and structure to allow
active composting with good air supply.
2. Acacia composts were well matured and
showed good physical characteristics as
partial substitutes for peat.
Evaluation of invasive Acacia species compost as alternative
horticultural organic substrates

68. Conclusions
3. With increasing composting time the
physical properties of the composts
improved, as well as the CEC, but the
same did not happen in relation to the
chemical characteristics such as pH or EC.
Evaluation of invasive Acacia species compost as alternative
horticultural organic substrates

69. Peat substitution by composts made with
cheap local resources such as biomass waste
from the control of invasive Acacia species
may contribute to bridge the gap between
poor and rich agricultural soil.
Evaluation of invasive Acacia species compost as alternative
horticultural organic substrates

71. Evaluation of physicochemical characteristics of invasive
Acacia waste cocomposted with pine bark for
horticultural use

72. Ground acacia biomass have sufficient
biodegradability and structure to allow
active composting with good air supply.
Results

73. 0
25
50
75
100
0 60 120 180 240 300 360 420 480
Temperature(C)
Composting time (days)
Ta A top A centre A base
Temperatures were kept between 60 ºC
and 75 ºC for several months
Pile A (Acacia and pine bark)
60°C

74. 0
25
50
75
100
0 60 120 180 240 300 360 420 480
Temperature(C)
Composting time (days)
Ta B top B centre B base
Pile B (Acacia and pine bark)
Time-temperature conditions exceeded the more
stringent criteria for complete pathogen
inactivation
60°C

75. Dry matter content (%)
A 36
B 39
Similar to the mean DM content (39%) of 16
commercial substrates evaluated by Brito et
al. (2010)

76. Bulk density (g cm-3)
A 0.25 ± 0.01
B 0.26 ± 0.01
Below the upper limit of 0.4 g cm-3 recommended
by Abad et al. (2001) laying also within the range
from 0.1 to 0.3 g cm-3 acceptable for seed
germination and plant propagation (Kämpf, 2000).

77. Real density (g cm-3)
A 1.70 ± 0.06
B 1.69 ± 0.03
Within the range of 1,4 - 2,0 g cm-3 recommended
by Abad et al. (2001)

78. Total pore space (% v/v)
A 85.3 ± 1.2
B 85.1 ± 0.9
Over 85% of the total volume of the substrate as
recommended by Verdonck and Gabriëls (1992)

79. Volume shrinkage (%, v)
A 16.0 ± 4.9
B 18.4 ± 3.7
Below the upper limit value (30% v/v)
recommended for horticultural substrates (Abad et
al., 2001)

80. 0
5
10
15
20
25
30
<0,125
0,125_0,25
0,25_0,5
0,5_1
1_2
2_5
5_10
10_16
>16
Weight(%)
Particle size (mm)
A B
Compost
Particles between 0.25 and 2.5 mm are
recommended to allow water supply and
adequate ventilation (Abad et al., 2001).

81. 0
20
40
60
80
100
A B
Volume(%)
Compost
Air capacity
Easily available water
Buffering capacity
Less available water
Dry solids
Dry solids of composts (14.7% and 14.9% v/v, respectively for
compost A and B) were within recommended values by
Verdonck and Gabriëls (1992).

82. 0
20
40
60
80
100
A B
Volume(%)
Compost
Air capacity
Easily available water
Buffering capacity
Less available water
Dry solids
Composts air capacity (> 23% v/v) contributed to high compost
macroporosity due to pine bark particles which are difficult to
degrade, and was above the minimum off 20% recommended by
Abad et al. (2001).

83. 0
20
40
60
80
100
A B
Volume(%)
Compost
Air capacity
Easily available water
Buffering capacity
Less available water
Dry solids
Less available water was similar to the mean of 16
commercial substrates evaluated by Brito et al. (2010)

84. 0
20
40
60
80
100
A B
Volume(%)
Compost
Air capacity
Easily available water
Buffering capacity
Less available water
Dry solids
The water buffering capacity of composts was equal to or
greater than the minimum limit of 4% recommended by de
Boot and Verdonck (1972) as ideal for horticultural
substrates

85. 0
20
40
60
80
100
A B
Volume(%)
Compost
Air capacity
Easily available water
Buffering capacity
Less available water
Dry solids
However, the easily available water (EAW) of composts
(16% and 19% respectively for compost A and B) was
slightly below the minimum value of 20% recommended by
Boot and Verdonck (1972)

86. 0
20
40
60
80
100
A B
Volume(%)
Compost
Air capacity
Easily available water
Buffering capacity
Less available water
Dry solids
Water holding capacity
The total water-holding capacity was suitable compared to the
minimum recommended values of 55% (Noguera et al., 2003) and
60% (Abad et al., 2001) for substrates.

87. 0
20
40
60
80
100
A B
Volume(%)
Compost
Easily available water
Buffering capacity
Less available water
The total water-holding capacity was suitable compared to the
minimum recommended values of 55% (Noguera et al., 2003) and
60% (Abad et al., 2001) for substrates.

88. pH
A 6.9 ± 0.1
B 6.3 ± 0.2
The pH value for compost B was slightly acidic and within
pH values set by Abad et al. (2001) for commercial
substrates (5.3 – 6.5). Both composts showed a pH value
within established optimal values (5.2 to 7.0) by Herrera
et al. (2008) for the growth of most greenhouse crops.

89. pH
A 6.9 ± 0.1
B 6.3 ± 0.2
Although the pH may limit compost use as single
substrate constituent, these composts showed lower
pH values compared to other recommended composts
for substrate composition, from bovine manure or
municipal solid waste.

90. EC (dS m-1)
A 0.2 ± 0.03
B 0.7 ± 0.10
The electrical condutivity of both piles was near
the maximum recommended value (0.5 dS m-1) by
Abad et al. (2001)

91. EC (dS m-1)
A 0.2 ± 0.03
B 0.7 ± 0.10
And considerably lower compared to other
composts that have been recommended for
mixing with peat in substrate composition, as
composts of cow dung or agro-industrial residues.

92. EC (dS m-1)
A 0.2 ± 0.03
B 0.7 ± 0.10
Therefore, EC of Acacia with bark composts may
potentially expand the end-use of these composts
to horticultural nursery applications

93. CEC (cmol+ kg-1 OM)
A 216 ± 56
B 204 ± 37
The CEC was above values found for common
commercial substrates (Brito et al., 2010)
recommended for
pot plant production (92 cmol+ kg-1 OM) cultivation
bags (85 cmol+ kg-1 OM) and peat blocks or plug trays
(152 cmol+ kg-1 OM).

94. CEC (cmol+ kg-1 OM)
A 216 ± 56
B 204 ± 37
The high CEC is important from an agronomic
perspective because it enhances the overall
fertilizer properties of the final compost.

95. OM content (g kg-1 DM)
A 676 ± 22
B 688 ± 10
OM contente was lower compared to most
comercial substrates based on peat.

96. C/N ratio
A 40 ± 1.0
B 41 ± 3.3
the C/N ratio of Acacia with bark composts was
similar to the average C/N ratio (C/N = 39) of the
16 commercial substrates previously evaluated by
Brito et al., 2010.

97. NH4
+–N / NO3
-–N ratio
A < 0.3
B < 1.0
The NH4
+–N / NO3
-–N ratio of compost A was below
the recommended maximum value of 0.5 (CCQC,
2001), therefore final compost A attained a fully
matured condition suitable for land application.

98. NH4
+–N / NO3
-–N ratio
A < 0.3
B < 1.0
Final compost from Pile B achieved the mineral N
stability ratio of <1 proposed by Larney and Hao
(2007), denoting a very stable or mature material.

99. N content (g kg-1 DM)
A 9.5
B 9.0
The final composts had low contents of N and P
compared to livestock and biowaste composts

100. P content (g kg-1 DM)
A 0.85
B 0.80
The final composts had low contents of N and P
compared to livestock and biowaste composts

101. K content (g kg-1 DM)
A 9.7
B 12.0
K content was within the typical ranges reported
in composts produced from a range of different
feedstock types (8.4 to 12.5 g kg−1).

102. Ca content (g kg-1 DM)
A 23.3
B 21.7
Interestingly, the Acacia with bark mixture
provided a particularly rich source of Ca which is
important for plant nutrition because of the slow
Ca mobility.

103. Conclusions (1/4)
Acacia with bark composts showed
high-quality physical characteristics
to replace peat moss in substrate
formulation

104. Compost chemical characteristics, such as pH and EC,
were appropriate for substrate constituents compared
to other domestic, industrial and livestock waste
composts that have been recommended for mixing
with peat in substrate composition.
Conclusions (2/4)

105. Compost CEC capacity and C/N ratio values were
suitable for substrate composition and the NH4
+–
N to NO3
-–N ratio in composted products
suggested a stable or mature material.
Conclusions (3/4)

106. Crop and container characteristics must be considered
for recommendations about the optimum proportion
of Acacia with bark compost in final substrate
composition.
Conclusions (4/4)

107. Thank you for your attention