Role of Digestate and Biochar in Carbon-Negative Bioenergy

Breunig, Hanna; Amirebrahimi, Jahon; Smith, Sarah; Scown, Corinne D.

doi:10.1021/acs.est.9b03763

Cited by 40 publications

(18 citation statements)

References 53 publications

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“…C-rich organic amendments (e.g. biochar) with a potential to sequester C [ 7 ] could be applied together with digestate and compensate this disadvantage by higher stabilization of both C [ 8 ] and N [ 9 ]. It was reported that amendment of digestate and biochar increased both total organic carbon (TOC) and soil C turnover in comparison to the sole digestate application [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of carbon-enriched digestate on the microbial soil activity

et al. 2021

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Objectives As a liquid organic fertilizer used in agriculture, digestate is rich in many nutrients (i.e. nitrogen, phosphorus, sulfur, calcium, potassium); their utilization may be however less efficient in soils poor in organic carbon (due to low carbon:nitrogen ratio). In order to solve the disadvantages, digestate enrichment with carbon-rich amendments biochar or humic acids (Humac) was tested. Methods Soil variants amended with enriched digestate: digestate + biochar, digestate + Humac, and digestate + combined biochar and humic acids—were compared to control with untreated digestate in their effect on total soil carbon and nitrogen, microbial biomass carbon, soil respiration and soil enzymatic activities in a pot experiment. Yield of the test crop lettuce was also determined for all variants. Results Soil respiration was the most significantly increased property, positively affected by digestate + Humac. Both digestate + biochar and digestate + Humac significantly increased microbial biomass carbon. Significant negative effect of digestate + biochar (compared to the control digestate) on particular enzyme activities was alleviated by the addition of humic acids. No significant differences among the tested variants were found in the above-ground and root plant biomass. Conclusions The tested organic supplements improved the digestate effect on some determined soil properties. We deduced from the results (carbon:nitrogen ratio, microbial biomass and activity) that the assimilation of nutrients by plants increased; however, the most desired positive effect on the yield of crop biomass was not demonstrated. We assume that the digestate enrichment with organic amendments may be more beneficial in a long time-scaled trial.

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Section: Introductionmentioning

confidence: 99%

Effect of carbon-enriched digestate on the microbial soil activity

et al. 2021

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“…Other studies confirm the positive effect of biogas systems and digestate application on SOC formation in general (Breunig, Amirebrahimi, Smith, & Scown, 2019; Franko & Witing, 2020; O'Keeffe et al., 2019; Prays & Franko, 2018; Witing et al., 2018). Studies comparing residue incorporation and biogas digestate application report a higher SOC formation in the latter case (Chen et al., 2012; Nielsen et al., 2020).…”

Section: Discussionmentioning

confidence: 75%

Straw utilization for biofuel production: A consequential assessment of greenhouse gas emissions from bioethanol and biomethane provision with a focus on the time dependency of emissions

2020

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The shift from straw incorporation to biofuel production entails emissions from production, changes in soil organic carbon (SOC) and through the provision of (co‐)products and entailed displacement effects. This paper analyses changes in greenhouse gas (GHG) emissions arising from the shift from straw incorporation to biomethane and bioethanol production. The biomethane concept comprises comminution, anaerobic digestion and amine washing. It additionally provides an organic fertilizer. Bioethanol production comprises energetic use of lignin, steam explosion, enzymatic hydrolysis and co‐fermentation. Additionally, feed is provided. A detailed consequential GHG balance with in‐depth focus on the time dependency of emissions is conducted: (a) the change in the atmospheric load of emissions arising from the change in the temporal occurrence of emissions comparing two steady states (before the shift and once a new steady state has established); and (b) the annual change in overall emissions over time starting from the shift are assessed. The shift from straw incorporation to biomethane production results in net changes in GHG emissions of (a) −979 (−436 to −1,654) and (b) −955 (−220 to −1,623) kg CO2‐eq. per tdry matter straw converted to biomethane (minimum and maximum). The shift to bioethanol production results in net changes of (a) −409 (−107 to −610) and (b) −361 (57 to −603) kg CO2‐eq. per tdry matter straw converted to bioethanol. If the atmospheric load of emissions arising from different timing of emissions is neglected in case (a), the change in GHG emissions differs by up to 54%. Case (b) reveals carbon payback times of 0 (0–49) and 19 (1–100) years in case of biomethane and bioethanol production, respectively. These results demonstrate that the detailed inclusion of temporal aspects into GHG balances is required to get a comprehensive understanding of changes in GHG emissions induced by the introduction of advanced biofuels from agricultural residues.

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“…The flux measured from the CRDS is in gas units using equation (1), which is then converted into mass concentration (mg/time) using the Ideal Gas Law in equation (2). We converted J to calculate the cumulative emissions to mass/g soil basis.…”

Section: Flux Measurements and Calculationsmentioning

confidence: 99%

“…For this study, we examined the impact of supplementing the traditional land application of manure with anaerobic digestate (AD) on soil GHG emissions of CO2 and N2O. AD is the decomposition process of organic matter without the presence of oxygen 2 . It is low in carbon, nutrient-rich, and may increase net primary productivity of crops and increase carbon sequestration in soils 3 .…”

Section: Introductionmentioning

confidence: 99%

Evaluating Greenhouse Gas Emissions From Soil Application of Anaerobic Organic Digestive Compared With Conventional Manure

Abonce¹,

Zhao²,

Rodrigues³

et al. 2020

UC Riverside Undergraduate Research Journal Submit

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The state of California is investing in anaerobic digesters to reduce methane emissions from agriculture. However, little is known about the impact of anaerobic digesters on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from soils after land application of digestate. The purpose of this study was to compare soil CO2 and N2O emission fluxes from anaerobic digestate treatment in conjunction with manure, manure treatment, and a control group without treatment on agricultural soils from two dairy farms. In addition to comparing treatments and sites, we tested the effects of temperature at either 23°C or 28°C to compare predicted future average temperatures. Soil samples were placed in mason jars with 18 jars per location: three manure treatments x 2, temperatures x 3 replications per treatment, and incubated for six weeks according to the temperature treatment. Soils were watered once a week to maintain 65% water holding capacity. Cavity ring-down spectrometers were used to collect gas emissions in a closed-loop system, and elemental analyzers were used to evaluate soil and treatment nutrient composition. We hypothesized that three main variables -manure, lower temperatures, and soils with low-nutrient content in conjunction with anaerobic digestate would all lead to lower emissions. Anaerobic digestate has been found to reduce greenhouse gas emissions while also being a nutrient-rich energy source. Microbial soil communities are also more active in warmer temperatures, which may increase the production of gas emissions. Overall, the results were inconclusive for either argument.

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Role of Digestate and Biochar in Carbon-Negative Bioenergy

Cited by 40 publications

References 53 publications

Effect of carbon-enriched digestate on the microbial soil activity

Effect of carbon-enriched digestate on the microbial soil activity

Straw utilization for biofuel production: A consequential assessment of greenhouse gas emissions from bioethanol and biomethane provision with a focus on the time dependency of emissions

Evaluating Greenhouse Gas Emissions From Soil Application of Anaerobic Organic Digestive Compared With Conventional Manure

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