Abstract
The thermal conversion of municipal sewage sludge (MSS) offers significant potential for sustainable waste management, particularly through the production of biochar. This study investigates the properties and soil application effects of three biochar types produced via pyrolysis: (i) pure sewage sludge (100%), (ii) sewage sludge blended with sawdust (50%+50%), and (iii) sewage sludge combined with sawdust and zeolite (50%+45%+5%). These biochars were applied at rates of 2.5% and 7.5% (w/w) to arable soil and assessed in an 8-week greenhouse experiment using lettuce (Lactuca sativa L. var. Brilant) as a model crop. The sewage sludge biochar was characterized by high nitrogen, phosphorus, and water-extractable calcium but exhibited low organic matter and organic carbon content. It enhanced soil enzyme activities related to carbon and nitrogen mineralization without affecting microbial respiration. However, at 7.5% application rate, this biochar caused the highest chlorophyll b content in lettuce, despite acidifying the soil. Adding sawdust to the pyrolysis feedstock significantly increased organic matter, organic carbon (with reduced recalcitrance), and the C: N ratio of biochar. This biochar formulation promoted microbial activity (as indicated by changes in soil respiration) and nutrient cycling, particularly through increased glucosidase activity. Conversely, addition of zeolite to the pyrolysis feedstock reduced the organic matter and organic carbon content while increasing biochar recalcitrance and nutrient immobilization, particularly of sulfur, ammonium, phosphorus, and calcium. At the 7.5% dose, the sawdust + zeolite-enriched biochar improved soil pH and potentially enhanced nutrient retention. However, it did not stimulate microbial enzyme activity or respiration, leading to lower photosynthetic pigment levels and reduced biomassin lettuce, especially at higher application rate. For short-term soil applications under the conditions of this pot trial, the sewage sludge-sawdust biochar demonstrated the most beneficial effects, rapidly stimulating microbial activity and nutrient transformation. In contrast, the sewage sludge-sawdust-zeolite biochar limited nutrient availability and plant growth, suggesting it may be less suitable for immediate soil and plant nutrition. Long-term studies are needed to fully assess the implications of these biochar types for sustainable agriculture. This study highlights the importance of feedstock composition and selection in tailoring biochar properties to meet specific soil and crop requirements.
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Claims 17
Claim · model-written summary
Pure sewage-sludge biochar had high nitrogen, phosphorus, and water-extractable calcium.
- Taxon
- lettuce
Lactuca sativae1 - Treatment
- sewage sludge biochare0
- Outcome
- high nitrogen, phosphorus, and water-extractable calciume0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The sewage sludge biochar was characterized by high nitrogen, phosphorus, and water-extractable calcium”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Pure sewage-sludge biochar had low organic matter and organic carbon.
- Taxon
- lettuceLactuca sativae1
- Treatment
- sewage sludge biochare0
- Outcome
- low organic matter and organic carbon contente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sewage sludge biochar was characterized by high nitrogen, phosphorus, and water-extractable calcium but exhibited low organic matter and organic carbon content”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Pure sewage-sludge biochar enhanced carbon- and nitrogen-mineralization enzyme activities.
- Taxon
- lettuceLactuca sativae2
- Treatment
- sewage sludge biochare1
- Outcome
- soil enzyme activities related to carbon and nitrogen mineralizatione0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It enhanced soil enzyme activities related to carbon and nitrogen mineralization”
e1“The sewage sludge biochar”
e2“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Pure sewage-sludge biochar did not affect microbial respiration.
- Taxon
- lettuceLactuca sativae2
- Treatment
- sewage sludge biochare1
- Outcome
- microbial respiratione0
- Direction
- without affectinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“without affecting microbial respiration”
e1“The sewage sludge biochar”
e2“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
At 7.5% application, pure sludge biochar produced the highest lettuce chlorophyll b content.
- Taxon
- lettuceLactuca sativae2
- Treatment
- sewage sludge biochare1
- Outcome
- chlorophyll b contente0
- Direction
- higheste0
- Qualifier
- 7.5% application ratee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at 7.5% application rate, this biochar caused the highest chlorophyll b content in lettuce”
e1“The sewage sludge biochar”
e2“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Pure sludge biochar acidified soil.
- Taxon
- lettuceLactuca sativae2
- Treatment
- sewage sludge biochare1
- Outcome
- soile0
- Direction
- acidifyinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite acidifying the soil”
e1“The sewage sludge biochar”
e2“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Adding sawdust increased biochar organic matter, organic carbon, and C:N ratio.
- Taxon
- lettuceLactuca sativae1
- Treatment
- Adding sawdust to the pyrolysis feedstocke0
- Outcome
- organic matter, organic carbon (with reduced recalcitrance), and the C: N ratio of biochare0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Adding sawdust to the pyrolysis feedstock significantly increased organic matter, organic carbon (with reduced recalcitrance), and the C: N ratio of biochar”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Sawdust-blended biochar promoted microbial activity and nutrient cycling, including increased glucosidase activity.
- Taxon
- lettuceLactuca sativae2
- Treatment
- Adding sawdust to the pyrolysis feedstocke1
- Outcome
- microbial activity (as indicated by changes in soil respiration) and nutrient cyclinge0
- Direction
- promotede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This biochar formulation promoted microbial activity (as indicated by changes in soil respiration) and nutrient cycling, particularly through increased glucosidase activity”
e1“Adding sawdust to the pyrolysis feedstock”
e2“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Adding zeolite reduced biochar organic matter and organic carbon.
- Taxon
- lettuceLactuca sativae1
- Treatment
- addition of zeolite to the pyrolysis feedstocke0
- Outcome
- organic matter and organic carbon contente0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“addition of zeolite to the pyrolysis feedstock reduced the organic matter and organic carbon content”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Adding zeolite increased biochar recalcitrance and immobilization of sulfur, ammonium, phosphorus, and calcium.
- Taxon
- lettuceLactuca sativae1
- Treatment
- addition of zeolite to the pyrolysis feedstocke0
- Outcome
- biochar recalcitrance and nutrient immobilization, particularly of sulfur, ammonium, phosphorus, and calciume0
- Direction
- increasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“addition of zeolite to the pyrolysis feedstock reduced the organic matter and organic carbon content while increasing biochar recalcitrance and nutrient immobilization, particularly of sulfur, ammonium, phosphorus, and calcium”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
At 7.5%, sawdust-zeolite biochar improved soil pH.
- Taxon
- lettuceLactuca sativae1
- Treatment
- sawdust + zeolite-enriched biochare0
- Outcome
- soil pHe0
- Direction
- improvede0
- Qualifier
- 7.5% dosee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the 7.5% dose, the sawdust + zeolite-enriched biochar improved soil pH”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
At 7.5%, sawdust-zeolite biochar potentially enhanced nutrient retention.
- Taxon
- lettuceLactuca sativae1
- Treatment
- sawdust + zeolite-enriched biochare0
- Outcome
- nutrient retentione0
- Direction
- enhancede0
- Qualifier
- potentiallye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the 7.5% dose, the sawdust + zeolite-enriched biochar improved soil pH and potentially enhanced nutrient retention”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Sawdust-zeolite biochar did not stimulate microbial enzyme activity or respiration.
- Taxon
- lettuceLactuca sativae2
- Treatment
- sawdust + zeolite-enriched biochare1
- Outcome
- microbial enzyme activity or respiratione0
- Direction
- did not stimulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it did not stimulate microbial enzyme activity or respiration”
e1“sawdust + zeolite-enriched biochar”
e2“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
Sawdust-zeolite biochar lowered lettuce photosynthetic pigments.
- Taxon
- lettuceLactuca sativae0
- Treatment
- sawdust + zeolite-enriched biochare1
- Outcome
- photosynthetic pigment levelse0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leading to lower photosynthetic pigment levels and reduced biomassin lettuce”
e1“sawdust + zeolite-enriched biochar”
Claim · model-written summary
Sawdust-zeolite biochar reduced lettuce biomass, especially at higher application rate.
- Taxon
- lettuceLactuca sativae0
- Treatment
- sawdust + zeolite-enriched biochare1
- Outcome
- biomassin lettucee0
- Direction
- reducede0
- Qualifier
- especially at higher application ratee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower photosynthetic pigment levels and reduced biomassin lettuce, especially at higher application rate”
e1“sawdust + zeolite-enriched biochar”
Claim · model-written summary
The authors judge sludge-sawdust biochar most beneficial for short-term soil application.
- Taxon
- lettuceLactuca sativae1
- Outcome
- sewage sludge-sawdust biochar demonstrated the most beneficial effectse0
- Qualifier
- short-term soil applications under the conditions of this pot triale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For short-term soil applications under the conditions of this pot trial, the sewage sludge-sawdust biochar demonstrated the most beneficial effects”
e1“lettuce (Lactuca sativa L. var. Brilant)”
Claim · model-written summary
The authors consider sludge-sawdust-zeolite biochar less suitable for immediate soil and plant nutrition.
- Taxon
- lettuceLactuca sativae1
- Outcome
- less suitable for immediate soil and plant nutritione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sewage sludge-sawdust-zeolite biochar limited nutrient availability and plant growth, suggesting it may be less suitable for immediate soil and plant nutrition”
e1“lettuce (Lactuca sativa L. var. Brilant)”
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See all 36 papers →8 of 15 groups shown: named compounds and organisms first, then groups whose results differ (checked claim by claim), then those with positive and negative results, then the smaller groups.
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.