Techno-economic analysis of biogas upgrading

Author(s): Mary Akingbasote, Dan Ciolkosz, Juliana Vasco, Guojie Wang

Abstract:

Water scrubbing is a physical absorption method which uses absorption to remove impurities from biogas. The feasibility of water scrubbing to upgrade biogas was analyzed for two fluids (tap water and digestate liquid), and in two settings (U.S and Nigeria). Experiments were carried out to test the absorption capacity of carbon dioxide using these fluids. A techno-economic model was created to simulate the performance of a biogas upgrading system, and the model was used to estimate the viability of the system.

Results indicate that biogas upgrading for a small-scale farm in Pennsylvania yields a negative net present value (NPV) of -$795,246, with all but the most optimistic scenario producing negative values. Sensitivity analysis indicates that pipeline cost, number of cows, and biogas production costs have the greatest impact on NPV, while utility costs have the least influence.

Digestate liquid can be used to absorb carbon dioxide; however, its performance is lower than that of water. It was found to be most effective at 4°C and 1440 minutes. The techno-economic analysis of using digestate liquid for upgrading also results in a slightly improved but still negative NPV (-$65,240), compared to using water, despite no associated cost for the liquid. This outcome can be attributed to the required height of the column, which is approximately twice the height needed when using water to achieve the same carbon dioxide removal efficiency.

Techno-economic analysis of biogas upgrading in Nigeria using biomethane as a substitute for liquefied petroleum gas (LPG), with a base case of 60 cows, also yields a negative NPV of -N10,253,874, only the most optimistic variations of this scenario result in a positive NPV. While the NPV of these systems tends to be negative, their use may be justifiable in favorable settings and conditions. Sensitivity analysis shows that the biogas production cost has the greatest impact on NPV, followed by compressed biomethane cost and the number of cows. However, biogas production costs could be reduced through funding incentives, grants, and financing mechanisms. The farming system in Nigeria also affects the availability of manure, as cows are not typically confined to a single location.

Overall, this thesis provides an assessment of the economic and technical feasibility of biogas upgrading using water and digestate liquid in two different continents, showing the significant variables assessing the adoption of the use of biomethane as electricity, renewable natural gas or liquified petroleum.

Funder: USDA NIFA

Award Title:

Consortium for Cultivating Human And Naturally reGenerative Enterprises: Grass2Gas

Award Number: 2020-68012-31824

Keywords:

biogas upgrading, carbon dioxide absorption, digestate liquid, geoscientific information, techno-economic analysis, water scrubbing

Project (Abbreviated name):

G2G_Ciolkosz_TEA_of_biogas_upgrading

Team: Grass2Gas

Full Metadata:

G2G_Ciolkosz_TEA_of_biogas_upgrading metadata_v1.1.pdf (219.66 KB)

Data Mirror:

Data Table Column Names and Descriptions

Table name	Column name	Data type	Units	Column description
data.dataset_carbon_dioxide_absorption_by_pH	carbon dioxide absorbed g	float	gram	The amount of carbon dioxide absorbed, expressed in grams.
data.dataset_carbon_dioxide_absorption_by_pH	carbon dioxide absorbed mol	float	mole	The amount of carbon dioxide absorbed, expressed in moles.
data.dataset_carbon_dioxide_absorption_by_pH	change in hydrogen ion molar	float	molePerLiter	The change in hydrogen ions, calculated as 10^-ph at the start subtracted from 10^-ph at the end.
data.dataset_carbon_dioxide_absorption_by_pH	change in pH	float	NA	The inital pH subtracted from the final pH.
data.dataset_carbon_dioxide_absorption_by_pH	dataset carbon dioxide absorption by pH pkey	integer	dimensionless	A unique primary key for this table.
data.dataset_carbon_dioxide_absorption_by_pH	method	string	NA	The method used to measure carbon dioxide absorption.
data.dataset_carbon_dioxide_absorption_by_pH	replicate	float	number	Each combination of sample, method, time interval, and temperature was replicated three times.
data.dataset_carbon_dioxide_absorption_by_pH	sample	string	NA	The liquid used to absorb carbon dioxide, either liquid digestate or water.
data.dataset_carbon_dioxide_absorption_by_pH	temperature celsius	float	celsius	The temperature the sample was heated to during absorption.
data.dataset_carbon_dioxide_absorption_by_pH	time interval minutes	float	minute	The length of time between introducing carbon dioxide to the sample and recording the outcome.
data.dataset_carbon_dioxide_absorption_by_volume	carbon dioxide absorbed g	float	gram	The amount of carbon dioxide absorbed, expressed in grams.
data.dataset_carbon_dioxide_absorption_by_volume	carbon dioxide absorbed mol	float	mole	The amount of carbon dioxide absorbed, expressed in moles.
data.dataset_carbon_dioxide_absorption_by_volume	change in volume mL	integer	milliliter	The change in sample volume after absorption, expressed in milliliters.
data.dataset_carbon_dioxide_absorption_by_volume	dataset carbon dioxide absorption by volume pkey	integer	dimensionless	A unique primary key for this table.
data.dataset_carbon_dioxide_absorption_by_volume	method	string	NA	The method used to measure carbon dioxide absorption.
data.dataset_carbon_dioxide_absorption_by_volume	replicate	float	number	Each combination of sample, method, time interval, and temperature was replicated three times.
data.dataset_carbon_dioxide_absorption_by_volume	sample	string	NA	The liquid used to absorb carbon dioxide, either liquid digestate or water.
data.dataset_carbon_dioxide_absorption_by_volume	temperature celsius	float	celsius	The temperature the sample was heated to during absorption.
data.dataset_carbon_dioxide_absorption_by_volume	time interval minutes	float	minute	The length of time between introducing carbon dioxide to the sample and recording the outcome.