3.     Revenue

Disaggregated Revenue by Product Technology

The following table presents our revenues disaggregated by product technology:

Disaggregated Revenue by Geography

The following table presents our revenues disaggregated by geography, based on the location of the end-user:

Timing of Revenue Recognition

The following table presents the timing of our revenue recognition:

Contract Balances

The timing of revenue recognition, billings, and cash collections results in billed accounts receivable, unbilled receivables (contract assets), and customer advances and deposits (contract liabilities) on the Condensed Consolidated Balance Sheets. In our Air Pollution Control (APC) technology segment, amounts are billed as work progresses in accordance with agreed-upon contractual terms. Generally, billing occurs subsequent to revenue recognition, resulting in contract assets. These assets are reported on the Condensed Consolidated Balance Sheets on a contract-by-contract basis at the end of each reporting period. At June 30, 2026,  December 31, 2025, and December 31, 2024, contract assets for APC technology projects were approximately $1,223, $887, and $2,075, respectively, and are included in accounts receivable on the Condensed Consolidated Balance Sheets.

The Company will periodically bill in advance of costs incurred before revenue is recognized, resulting in contract liabilities. These liabilities are reported on the Condensed Consolidated Balance Sheets on a contract-by-contract basis at the end of each reporting period. Contract liabilities were $960, $1,026, and $721 at June 30, 2026,  December 31, 2025, and December 31, 2024, respectively, and are included in other accrued liabilities on the Condensed Consolidated Balance Sheets.

Changes in the contract asset and liability balances during the six-month period ended June 30, 2026 were not materially impacted by any other items other than amounts billed and revenue recognized as described previously. Revenue recognized that was included in the contract liability balance at the beginning of the period was $155 and $607 for the three and six months ended June 30, 2026, respectively, and $171 and $543 for the three and six months ended June 30, 2025, respectively, which represented revenue from progress towards completion of our APC technology contracts. 

As of June 30, 2026 and December 31, 2025, we had no construction contracts in progress that were identified as a loss contract. 

Remaining Performance Obligations

Remaining performance obligations represents the transaction price of APC technology booked orders for which work has not been performed. As of June 30, 2026, the aggregate amount of the transaction price allocated to remaining performance obligations was $14,308. The Company expects to recognize revenue on approximately $10,489 of the remaining performance obligations over the next 12 months with the remaining recognized thereafter. 

Accounts Receivable

The components of accounts receivable are as follows: