Commitments and Contingencies	12 Months Ended
Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. COMMITMENTS AND CONTINGENCIES Letters of Credit As of December 31, 2025 and 2024, the Company was required to maintain standby letters of credit totaling $15,504 and $15,120, respectively, to support obligations of certain Company subsidiaries. These letters of credit were issued in favor of a lender, utilities, a governmental agency, and an independent system operator under PPA electrical interconnection agreements, and in place of a debt service reserve. There have been no draws to date on these letters of credit. Guaranty Opal Paragon On September 13, 2024, OPAL Paragon entered into a tax credit purchasing agreement with Apollo Management Holdings, L.P., ("Buyer"), pursuant to which OPAL Paragon sold $11,096 investment tax credits to the buyer for net proceeds of $8,906. If the tax credits are disallowed or recaptured from the Buyer, OPAL Paragon will be required to return the purchase price and pay any taxes, interest or penalties incurred. On March 28, 2025, OPAL Paragon entered into a tax credit purchase agreement with the Buyer, pursuant to which OPAL Paragon sold $9,801 of investment tax credits to the Buyer for net proceeds of $8,037. If the tax credits are disallowed or recaptured from the Buyer, OPAL Paragon will be required to return the purchase price and pay any taxes, interest or penalties incurred. In connection with the above transaction, all of the obligations of OPAL Paragon under such tax credit purchase agreement are guaranteed by the Company. Opal Fuels LLC On June 20, 2025, OPAL Fuels LLC entered into tax credit purchase agreements with the Buyer and EagleBank, pursuant to which OPAL Fuels LLC sold $16,740 of investment tax credits for net proceeds of $13,686. If the tax credits are disallowed or recaptured from the Buyer, OPAL Fuels LLC will be required to return the purchase price and pay any taxes, interest or penalties incurred. On September 12, 2025, OPAL Fuels LLC entered into tax credit purchase agreements with the Buyer and Athene Annuity and Life Company, pursuant to which OPAL Fuels LLC sold $17,369 of investment tax credits for net proceeds of $14,567. If the tax credits are disallowed or recaptured from the Buyer, OPAL Fuels LLC will be required to return the purchase price and pay any taxes, interest or penalties incurred. In connection with the above transaction, all of the obligations of OPAL Fuels LLC under such tax credit purchase agreements are guaranteed by the Company. Legal Matters The Company is involved in various claims arising in the normal course of business. Management believes that the outcome of these claims will not have a material adverse effect on the Company's financial position, results of operations or cash flows. Set forth below is information related to the Company’s material pending legal proceedings as of the date of this report, other than ordinary routine litigation incidental to the business. There have been no material changes to such legal proceedings. Central Valley Project Direct Contractor Claims In September 2021, an indirect subsidiary of the Company, MD Digester, LLC (“MD”), entered into a fixed-price Engineering, Procurement and Construction Contract (an “EPC Contract”) with VEC Partners, Inc. d/b/a CEI Builders (“CEI”) for the design and construction of a turn-key renewable natural gas production facility using dairy cow manure as feedstock in California’s Central Valley. In December 2021, a second indirect subsidiary of the Company, VS Digester, LLC (“VS”) entered into a nearly identical EPC Contract (collectively, the "EPC Contracts") with CEI for the design and construction of a second facility, also in California’s Central Valley. CEI’s performance under both of the EPC Contracts is fully bonded by licensed sureties. CEI has submitted a series of change order requests seeking to increase the EPC Contract Price by approximately $14,000, per project, primarily due to: (1) modifications to CEI’s design drawings which are required to meet its contracted performance guaranties, and (2) a default by one of CEI’s major equipment manufacturers. The Company disputes the vast majority of the change order requests. In January 2024, the Company filed a civil lawsuit captioned, MD Digester, LLC. et. al. vs. VEC Partners, Inc. et. al.; with the California Superior Court, County of San Joaquin; Action No. STK- CV-UCC-2024-0000185 and commenced a related arbitration proceeding in order to obtain a formal determination on the claims; American Arbitration Association ("AAA") Case No. 01-24-0000-0775. The Superior Court Action has been stayed, pending the conclusion of the arbitration. In the meantime, the AAA has empaneled three experienced arbitrators and has set the hearing date for the matter, currently scheduled in May 2026. The EPC Agreement requires that CEI, continue working during the course of the litigation and related arbitration proceedings; however, CEI effectively stopped working. On June 26, 2024, MD issued a Notice of Default and Demand to Cure to CEI. CEI failed to do so, and on July 30, 2024, MD terminated CEI for default. MD notified CEI’s performance bond surety, Atlantic Specialty Insurance Company of the termination and demanded that it perform under the bond. Atlantic has denied the claim. Similarly, on July 11, 2024, VS issued a Notice of Default and Demand to Cure, advising CEI of its defaults and giving it an opportunity to cure. CEI failed to do so, and on August 27, 2024, VS terminated CEI for default. VS has notified CEI’s bond surety, also Atlantic, of the second termination and demanded that it perform under the bond. The surety has denied the claim. As a result of CEI’s default and Atlantic’s denial of the claims, MD and VS have amended their claims in the AAA arbitration to include breach of contract claims against CEI and breach of performance bond claims against Atlantic (who was formally joined into the arbitration on November 20, 2024) in the AAA Arbitration with CEI. CEI has since recorded mechanic’s liens against each of the projects for $4,948 (MD) and $1,984 (VS), and recently filed actions with the Stanislaus and San Joaquin County Superior Courts, respectively, to enforce their liens. It is expected that these claims will be stayed and consolidated with the pending arbitration proceeding. The AAA proceeding is scheduled for evidentiary hearing from May 4 through May 22, 2026. Based upon the deposition testimony and the expert reports that were exchanged on February 23, 2026, the Company reasonably believes that it will demonstrate that the terminations were justified and for cause. Issues related to damages, i.e., the cost to complete the projects, are evolving and it is premature to offer an opinion on the strength of this component of the case. Subcontractor Lien Claims In addition to the above-referenced action and arbitration, several of CEI’s subcontractors have recorded mechanic’s liens against the MD and VS projects for $3,141, which the Company is obligated to defend and indemnify the dairy owners from and against. Several of liens were untimely and have been released voluntarily by the claimants, others were released through the recording of release bonds by Company. The NWP Industries, L.P. ("NWP") and Argo Sales ("Argo") claims have been settled and will be dismissed as to MD and VS when the settlement payments have been fully funded. Former Development Partner/construction Manager In March 2024, the Company filed an action in the Orange County Superior Court (Case No. 30- 2024-01415510-CU-BC-CXC) against its former development partner and construction manager, Sierra Renewable Organics Management, LLC, as well as its principal (Ethan Werner) and affiliated engineering firm (CH Four Biogas) for Breach of Contract, Indemnity, Declaratory Relief, Intentional Misrepresentation and Negligent Misrepresentation relating to the design and development of the Projects. The defendants have recently filed an answer and certain cross claims, to which the Company has demurred. Discovery in the case is now underway.

As of December 31, 2025 and 2024, the Company was required to maintain standby letters of credit totaling $15,504 and $15,120, respectively, to support obligations of certain Company subsidiaries. These letters of credit were issued in favor of a lender, utilities, a governmental agency, and an independent system operator under PPA electrical interconnection agreements, and in place of a debt service reserve. There have been no draws to date on these letters of credit.

On September 13, 2024, OPAL Paragon entered into a tax credit purchasing agreement with Apollo Management Holdings, L.P., ("Buyer"), pursuant to which OPAL Paragon sold $11,096 investment tax credits to the buyer for net proceeds of $8,906. If the tax credits are disallowed or recaptured from the Buyer, OPAL Paragon will be required to return the purchase price and pay any taxes, interest or penalties incurred.

On March 28, 2025, OPAL Paragon entered into a tax credit purchase agreement with the Buyer, pursuant to which OPAL Paragon sold $9,801 of investment tax credits to the Buyer for net proceeds of $8,037. If the tax credits are disallowed or recaptured from the Buyer, OPAL Paragon will be required to return the purchase price and pay any taxes, interest or penalties incurred.

On June 20, 2025, OPAL Fuels LLC entered into tax credit purchase agreements with the Buyer and EagleBank, pursuant to which OPAL Fuels LLC sold $16,740 of investment tax credits for net proceeds of $13,686. If the tax credits are disallowed or recaptured from the Buyer, OPAL Fuels LLC will be required to return the purchase price and pay any taxes, interest or penalties incurred.

On September 12, 2025, OPAL Fuels LLC entered into tax credit purchase agreements with the Buyer and Athene Annuity and Life Company, pursuant to which OPAL Fuels LLC sold $17,369 of investment tax credits for net proceeds of $14,567. If the tax credits are disallowed or recaptured from the Buyer, OPAL Fuels LLC will be required to return the purchase price and pay any taxes, interest or penalties incurred.

In connection with the above transaction, all of the obligations of OPAL Fuels LLC under such tax credit purchase agreements are guaranteed by the Company.

The Company is involved in various claims arising in the normal course of business. Management believes that the outcome of these claims will not have a material adverse effect on the Company's financial position, results of operations or cash flows.

Set forth below is information related to the Company’s material pending legal proceedings as of the date of this report, other than ordinary routine litigation incidental to the business. There have been no material changes to such legal proceedings.

In September 2021, an indirect subsidiary of the Company, MD Digester, LLC (“MD”), entered into a fixed-price Engineering, Procurement and Construction Contract (an “EPC Contract”) with VEC Partners, Inc. d/b/a CEI Builders (“CEI”) for the design and construction of a turn-key renewable natural gas production facility using dairy cow manure as feedstock in California’s Central Valley. In December 2021, a second indirect subsidiary of the Company, VS Digester, LLC (“VS”) entered into a nearly identical EPC Contract (collectively, the "EPC Contracts") with CEI for the design and construction of a second facility, also in California’s Central Valley. CEI’s performance under both of the EPC Contracts is fully bonded by licensed sureties.

CEI has submitted a series of change order requests seeking to increase the EPC Contract Price by approximately $14,000, per project, primarily due to: (1) modifications to CEI’s design drawings which are required to meet its contracted performance guaranties, and (2) a default by one of CEI’s major equipment manufacturers. The Company disputes the vast majority of the change order requests.

In January 2024, the Company filed a civil lawsuit captioned, MD Digester, LLC. et. al. vs. VEC Partners, Inc. et. al.; with the California Superior Court, County of San Joaquin; Action No. STK- CV-UCC-2024-0000185 and commenced a related arbitration proceeding in order to obtain a formal determination on the claims; American Arbitration Association ("AAA") Case No. 01-24-0000-0775. The Superior Court Action has been stayed, pending the conclusion of the arbitration. In the meantime, the AAA has empaneled three experienced arbitrators and has set the hearing date for the matter, currently scheduled in May 2026.

The EPC Agreement requires that CEI, continue working during the course of the litigation and related arbitration proceedings; however, CEI effectively stopped working. On June 26, 2024, MD issued a Notice of Default and Demand to Cure to CEI. CEI failed to do so, and on July 30, 2024, MD terminated CEI for default. MD notified CEI’s performance bond surety, Atlantic Specialty Insurance Company of the termination and demanded that it perform under the bond. Atlantic has denied the claim.

Similarly, on July 11, 2024, VS issued a Notice of Default and Demand to Cure, advising CEI of its defaults and giving it an opportunity to cure. CEI failed to do so, and on August 27, 2024, VS terminated CEI for default. VS has notified CEI’s bond surety, also Atlantic, of the second termination and demanded that it perform under the bond. The surety has denied the claim.

As a result of CEI’s default and Atlantic’s denial of the claims, MD and VS have amended their claims in the AAA arbitration to include breach of contract claims against CEI and breach of performance bond claims against Atlantic (who was formally joined into the arbitration on November 20, 2024) in the AAA Arbitration with CEI.

CEI has since recorded mechanic’s liens against each of the projects for $4,948 (MD) and $1,984 (VS), and recently filed actions with the Stanislaus and San Joaquin County Superior Courts, respectively, to enforce their liens. It is expected that these claims will be stayed and consolidated with the pending arbitration proceeding.

The AAA proceeding is scheduled for evidentiary hearing from May 4 through May 22, 2026. Based upon the deposition testimony and the expert reports that were exchanged on February 23, 2026, the Company reasonably believes that it will demonstrate that the terminations were justified and for cause. Issues related to damages, i.e., the cost to complete the projects, are evolving and it is premature to offer an opinion on the strength of this component of the case.

In addition to the above-referenced action and arbitration, several of CEI’s subcontractors have recorded mechanic’s liens against the MD and VS projects for $3,141, which the Company is obligated to defend and indemnify the dairy owners from and against. Several of liens were untimely and have been released voluntarily by the claimants, others were released through the recording of release bonds by Company.

The NWP Industries, L.P. ("NWP") and Argo Sales ("Argo") claims have been settled and will be dismissed as to MD and VS when the settlement payments have been fully funded.