Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation

The consolidated financial statements include the accounts of Fuel Tech and its wholly owned subsidiaries. 

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (GAAP). The books and records of subsidiaries located in foreign countries are maintained according to generally accepted accounting principles in those countries. Upon consolidation, the Company evaluates the differences in accounting principles and determines whether adjustments are necessary to convert the foreign financial statements to the accounting principles upon which the consolidated financial statements are based. All intercompany transactions have been eliminated.

Geopolitical And Unexpected Events [Policy Text Block]

Geopolitical and Unexpected Events 

Management cannot predict the full impact of geopolitical and unexpected events which may impact new or existing projects and prices and availability of raw materials, energy and other materials. These events may also impact energy and regulatory policy nationally or regionally for the impacted regions. Such disruptions could have a material adverse effect on our business and financial results. The Company continues to monitor the potential impacts on the business.

Liquidity, Policy [Policy Text Block]

Liquidity

We have experienced net losses in recent years. We continue to monitor our liquidity needs and have taken measures to reduce expenses and restructure operations, which we feel are necessary to ensure we maintain sufficient working capital and liquidity to operate the business and invest in our future. As a result, we have evaluated our ongoing business needs, and considered the cash requirements of our APC and FUEL CHEM businesses. This evaluation included consideration of the following: a) customer and revenue trends in our APC and FUEL CHEM business segments, b) current operating structure and expenditure levels, c) current availability of working capital, and d) support for our research and development initiatives. We believe our current cash position and net cash flows expected to be generated from operations are adequate to fund planned operations of the Company.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

The preparation of the financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company uses estimates in accounting for, among other items, revenue recognition, allowance for credit losses, income tax provisions, excess and obsolete inventory reserve, impairment of long-lived assets, and warranty expenses. Actual results could differ from those estimates.

Fair Value Measurement, Policy [Policy Text Block]

Fair Value Measurements

The carrying values of cash and cash equivalents, accounts receivable, and accounts payable are reasonable estimates of their fair value due to their short-term nature.

We apply authoritative accounting guidance for fair value measurements of financial and non-financial assets and liabilities. This guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis and clarifies that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the standard establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

• Level 1 – Observable inputs to the valuation methodology such as quoted prices in active markets for identical assets or liabilities

• Level 2 – Inputs to the valuation methodology including quoted prices for similar assets or liabilities in active markets, quoted prices for identical assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability, and inputs that are derived principally from or corroborated by observable market data by correlation or other means

• Level 3 – Significant unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own estimates and assumptions or those expected to be used by market participants. Generally, these fair value measures are model-based valuation techniques such as discounted cash flows, option pricing models, and other commonly used valuation techniques

Transfers between levels of the fair value hierarchy are recognized based on the actual date of the event or change in circumstances that caused the transfer. We had no assets or liabilities that were valued using level 2 or level 3 inputs and therefore there were no transfers between levels of the fair value hierarchy during the periods ended December 31, 2023 and 2022.

Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]

Cash and cash equivalents

We consider all highly liquid debt investments with original maturities from the date of purchase of three months or less as cash equivalents. Cash equivalents include investments in money market funds. At December 31, 2023, we had cash on hand of approximately $601 at our Beijing, China subsidiary that is subject to certain local regulations that may limit the immediate availability of these funds outside of China. Cash on hand at our Italy subsidiary totaled approximately $821 at December 31, 2023. Cash on hand at our Chilean subsidiary totaled approximately $200 at December 31, 2023.

The following table provides a reconciliation of cash and cash equivalents reported within the Consolidated Balance Sheet that sum to the total of the same such amounts shown in the Consolidated Statements of Cash Flows:

	December 31, 2023		December 31, 2022
Cash	$	12,495	$	12,560
Cash equivalents		5,083		10,768
Total cash and cash equivalents shown in the Consolidated Statements of Cash Flows	$	17,578	$	23,328

Investment, Policy [Policy Text Block]

Investments

In June 2022, the Board of Directors approved a plan to invest up to $10,000 of excess capital in debt securities, or held in money market funds until such investments can be made, with BMO Harris Bank N.A (BMO Harris). In December 2022, the Board of Directors approved an additional transfer of $10,000 of excess capital into the investment account. A portion of the funds invested are restricted as collateral under the Investment Collateral Security agreement (see Note 11). At December 31, 2023, the amount of funds collateralized under the Investment Collateral Security agreement is $1,356 relating to existing standby letters of credit that is comprised of $904 with varying maturity dates and expire no later than November 30, 2025.

Our investments in debt securities consist of United States (US) Treasury securities, including Notes, Bonds, and Bills, and US Government Agency securities, which are designated as held-to-maturity (HTM) and stated at amortized cost. The Company has the positive intent and ability to hold these investments to maturity and does not expect to sell any debt securities before maturity to settle an obligation under the Investment Collateral Security agreement. The maturities of our HTM investments range from three to thirty-six months. HTM debt investments with original maturities of approximately three months or less from the date of purchase are classified within cash and cash equivalents. HTM debt investments with original maturities at the date of purchase greater than approximately three months and remaining maturities of less than one year are classified as short-term investments. HTM debt investments with remaining maturities beyond one year are classified as long-term investments. Interest income, including amortization of premium and accretion of discount, are included on the Consolidated Statements of Operations in Interest income under the effective yield method. Accrued interest is included in Prepaid expenses and other current assets on the Consolidated Balance Sheets. Due to the creditworthiness of the entities issuing these securities, there is no impairment recorded related to the unrealized losses.

The following table provides the amortized cost, gross unrealized gains and losses, and fair value of our HTM debt securities:

	December 31,
	2023			2022
Held-to-maturity debt securities:
Amortized cost	$	15,800		$	9,341
Gross unrecognized gains		—			—
Gross unrecognized losses		(86	)		(168	)
Fair value	$	15,714		$	9,173

The following table provides the amortized cost and fair value of debt securities by maturities at December 31, 2023:

	Amortized Cost		Fair Value
Within one year	$	12,136	$	12,056
After one year through two years		3,664		3,658
Total	$	15,800	$	15,714

Foreign Currency Risk Management [Policy Text Block]

Foreign Currency Risk Management

Our earnings and cash flows are subject to fluctuations due to changes in foreign currency exchange rates. We do not enter into foreign currency forward contracts or into foreign currency option contracts to manage this risk due to the nature of the transactions involved.

Accounts Receivable [Policy Text Block]

Accounts Receivable

Accounts receivable consist of amounts due to us in the normal course of our business, are not collateralized, and normally do not bear interest. Accounts receivable includes contract assets, billings occurring subsequent to revenue recognition under Accounting Standards Codification (ASC) 606 Revenue from Contracts with Customers. At December 31, 2023 and 2022, unbilled receivables were approximately $2,285 and $3,082, respectively. Refer to Note 2 for further detail.

Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block]

Allowance for Credit Losses

In June 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, and in November 2019, the FASB issued ASU 2019-10, Financial Instruments - Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842). This guidance requires the measurement of all expected losses based on historical experience, current conditions and reasonable and supportable forecasts. For trade receivables and other financial instruments, we are required to use a forward-looking expected loss model rather than the incurred loss model for recognizing credit losses which reflects losses that are probable. The Company adopted these ASUs on January 1, 2023 using the prospective method. Application of the amendments did not require a cumulative-effect adjustment to retained earnings as of the effective date and did not have a material impact on our financial statements. Beginning on January 1, 2023, Fuel Tech will use the caption Allowance for Credit Losses and our expected credit loss model to calculate the allowance.

For the general risk categories, the Company uses historical losses over a fixed period, excluding certain write-off activity that was not considered credit loss events, to determine the historical credit loss. Historical loss rates are then adjusted to consider current economic conditions, and past, current, and future events and circumstances when determining expected credit losses. Investments in financial assets issued by US Government and Government Agency are considered as having zero expected credit losses and are excluded from the allowance for credit loss calculation.

The allowance for credit losses is our management's best estimate of the amount of credit losses in accounts receivable. At the end of each reporting period, the allowance for credit losses balance is reviewed relative to management’s assessment and is adjusted if deemed necessary. Bad debt write-offs are made when management believes it is probable a receivable will not be recovered. The table below sets forth the components of the Allowance for Credit Losses for the years ended December 31.

Year	Balance at January 1		Provision charged to expense			Write-offs / Recoveries			Balance at December 31
2022	$	223	$	(19	)	$	(94	)	$	110
2023	$	110	$	24		$	(23	)	$	111

Prepaid Expenses and Other Current Assets [Policy Text Block]

Prepaid expenses and other current assets

Prepaid expenses and other current assets are short-term commitments of typically three to six months for future payments and can be redeemed at a discount or applied to future vendor payments.

Inventory, Policy [Policy Text Block]

Inventories

Inventories consist primarily of equipment constructed for resale and spare parts and are stated at the lower of cost or net realizable value, using the weighted-average cost method. At December 31, 2023 and 2022, inventory included equipment constructed for resale of$207 and $207, respectively, and spare parts, net of reserves of $232 and $185, respectively. Usage is recorded in cost of sales in the period that parts were issued to a project, used to service equipment, or sold to customers. Equipment constructed for resale that is in process is recorded in Other assets. In process equipment for inventory recorded as other assets was $618 and $634 as of December 31, 2023 and 2022, respectively.   

Inventories are periodically evaluated to identify obsolete or otherwise impaired parts and are written off when management determines usage is not probable. The Company estimates the balance of excess and obsolete inventory by analyzing inventory by age using last used and original purchase date and existing sales pipeline for which the inventory could be used. The table below sets forth the components of the Excess and Obsolete Inventory Reserve for the years ended December 31.

Year	Balance at January 1		Provision charged to expense			Write-offs / Recoveries			Balance at December 31
2022	$	927	$	—		$	—		$	927
2023	$	927	$	(56	)	$	(258	)	$	613

Foreign Currency Transactions and Translations Policy [Policy Text Block]

Foreign Currency Translation and Transactions

Assets and liabilities of consolidated foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at year end. Revenues and expenses are translated at average exchange rates prevailing during the year. Gains or losses on foreign currency transactions and the related tax effects are reflected in net loss. The resulting translation adjustments are included in stockholders’ equity as part of accumulated other comprehensive loss.

Accumulated Other Comprehensive Income (Loss), Policy [Policy Text Block]

Accumulated Other Comprehensive Loss

	December 31,
	2023			2022
Foreign currency translation
Balance at beginning of period	$	(1,728	)	$	(1,604	)
Other comprehensive loss:
Foreign currency translation adjustments (1)		(20	)		(124	)
Balance at end of period	$	(1,748	)	$	(1,728	)
Total accumulated other comprehensive loss	$	(1,748	)	$	(1,728	)

(1) In all periods presented, there were no tax impacts related to functional currency translation adjustments.

Research and Development Expense, Policy [Policy Text Block]

Research and Development

Research and development costs are expensed as incurred. Research and development projects funded by customer contracts are reported as part of cost of goods sold. Internally funded research and development expenses are reported as operating expenses.

Standard Product Warranty, Policy [Policy Text Block]

Product/System Warranty

We typically warrant our air pollution control products and systems against defects in design, materials and workmanship for one to two years. A provision for estimated future costs relating to warranty expense is recorded when the products/systems become commercially operational.

Goodwill and Intangible Assets, Policy [Policy Text Block]

Goodwill

Goodwill is evaluated for impairment at the reporting unit level, which is defined as an operating segment or one level below an operating segment. Goodwill of our reporting units is assigned upon acquisition after considering the nature of the net assets giving rise to the goodwill and how each reporting unit would enjoy the benefits and synergies of the net assets acquired. We have two reporting units for goodwill evaluation purposes: the FUEL CHEM technology reporting unit and the APC technology reporting unit. There is no goodwill associated with our APC technology reporting unit. The entire goodwill balance of $2,116 was allocated to the FUEL CHEM technology reporting unit as of December 31, 2023 and 2022.

Goodwill is tested for impairment at least annually as of the first day of our fourth quarter, or more frequently if events or changes in circumstances indicate that the carrying value may not be recoverable. Our evaluation of goodwill impairment involves first assessing qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. We may bypass this qualitative assessment, or determine that based on our qualitative assessment considering the totality of events and circumstances including macroeconomic factors, industry and market considerations, current and projected financial performance, a sustained decrease in our share price, or other factors, that additional impairment analysis is necessary. This additional analysis involves comparing the current fair value of our reporting units to their carrying values. We use a discounted cash flow (DCF) model to determine the current fair value of our FUEL CHEM reporting unit. A number of significant assumptions and estimates are involved in the application of the DCF model to forecast operating cash flows, including markets and market share, sales volumes and prices, costs to produce and working capital changes. Management considers historical experience and all available information at the time the fair values of its reporting units are estimated. However, actual fair values that could be realized in an actual transaction may differ from those used to evaluate the impairment of goodwill. Fuel Tech performed its annual goodwill impairment analysis as of October 1, 2023 and determined that no impairment of goodwill existed. The Company did not recognize a charge for goodwill impairment for the periods ended December 31, 2023 and 2022.

Other Intangible Assets

Management reviews other finite-lived intangible assets, patent assets, trade names, and lease assets for impairment when events or changes in circumstances indicate the carrying amount of an asset or asset group may not be recoverable. In the event that impairment indicators exist, a further analysis is performed and if the sum of the expected undiscounted future cash flows resulting from the use of the asset or asset group is less than the carrying amount of the asset or asset group, an impairment loss equal to the excess of the asset or asset group's carrying value over its fair value is recorded. Management considers historical experience and all available information at the time the estimates of future cash flows are made, however, the actual cash values that could be realized may differ from those that are estimated.

During the years ended December 31, 2023 and 2022, Fuel Tech recorded no patent or trademark abandonment charges.

Third-party costs related to the development of patents are included within other intangible assets on the consolidated balance sheets. The third-party costs capitalized as patent costs during the years ended December 31, 2023 and 2022 were $28 and $37, respectively. Third-party costs are comprised of legal fees that relate to the review and preparation of patent disclosures and filing fees incurred to present the patents to the required governing body.

Our intellectual property portfolio has been a significant building block for the APC and FUEL CHEM technology segments. The patents are essential to the generation of revenue for our businesses and are essential to protect us from competition in the markets in which we serve. These costs are being amortized on the straight-line method over the period beginning with the patent issuance date and ending on the patent expiration date. Patent maintenance fees are charged to operations as incurred.

Amortization expense from continuing operations for intangible assets was $61 and $88 for the years ended December 31, 2023 and 2022, respectively. The table below shows the amortization period and other intangible asset cost by intangible asset as of December 31, 2023 and 2022, and the accumulated amortization and net intangible asset value in total for all other intangible assets.

			2023							2022
Description of Other Intangibles	Amortization Period (years)		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Patent assets		1 - 20		826		(468	)		358		803		(406	)		397
Total			$	826	$	(468	)	$	358	$	803	$	(406	)	$	397

The table below shows the estimated future amortization expense for intangible assets:

Year	Estimated Amortization Expense
2024	$	54
2025		33
2026		32
2027		32
2028		32
Thereafter		175
Total	$	358

Property, Plant and Equipment, Policy [Policy Text Block]

Property and Equipment

Property and equipment is stated at historical cost and does not include capital in process expenditures yet to be capitalized. Provisions for depreciation are computed by the straight-line method, using estimated useful lives that range based on the nature of the asset. Leasehold improvements are depreciated over the shorter of the associated lease term or the estimated useful life of the asset. Depreciation expense was $281 and $352 for the years ended December 31, 2023 and 2022, respectively. The table below shows the depreciable life and cost by asset class as of December 31, 2023 and 2022, and the accumulated depreciation and net book value in total for all classes of assets.

Description of Property and Equipment	Depreciable Life (years)		2023			2022
Land			$	1,050		$	1,050
Building		39		3,950			3,950
Building and leasehold improvements		3 - 39		2,655			2,626
Field equipment		3 - 4		12,100			11,882
Computer equipment and software		2 - 3		2,049			2,117
Furniture and fixtures		3 - 10		1,307			1,306
Vehicles		5		32			32
Construction in process				99			29
Total cost				23,242			22,992
Less accumulated depreciation				(18,703	)		(18,557	)
Total net book value			$	4,539		$	4,435

Property and equipment is reviewed for impairment when events and circumstances indicate that the carrying amount of the assets (or asset group) may not be recoverable. If impairment indicators exist, we perform a more detailed analysis and an impairment loss is recognized when estimated future undiscounted cash flows expected to result from the use of the asset (or asset group) and its eventual disposition are less than the carrying amount. This process of analyzing impairment involves examining the operating condition of individual assets (or asset group) and estimating a fair value based upon current condition, relevant market factors and remaining estimated operational life compared to the asset’s remaining depreciable life. Quoted market prices and other valuation techniques are used to determine expected cash flows.

Revenue [Policy Text Block]

Revenue Recognition

The Company recognizes revenue when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. The majority of our contracts have a single performance obligation as the promise to transfer the individual goods or services is not separately identifiable from other promises in the contracts and, therefore, not distinct. Revenue is measured as the amount of consideration we expect to receive in exchange for transferring goods or providing services. Sales, value add, and other taxes we collect concurrent with revenue-producing activities are excluded from revenue.

Air Pollution Control Technology

Fuel Tech’s APC contracts are typically six to eighteen months in length. A typical contract will have three or four critical operational measurements that, when achieved, serve as the basis for us to invoice the customer via progress billings. At a minimum, these measurements will include the generation of engineering drawings, the shipment of equipment and the completion of a system performance test.

As part of most of its contractual APC project agreements, Fuel Tech will agree to customer-specific acceptance criteria that relate to the operational performance of the system that is being sold. These criteria are determined based on modeling that is performed by Fuel Tech personnel, which is based on operational inputs that are provided by the customer. The customer will warrant that these operational inputs are accurate as they are specified in the binding contractual agreement. Further, the customer is solely responsible for the accuracy of the operating condition information; typically all performance guarantees and equipment warranties granted by us are voidable if the operating condition information is inaccurate or is not met.

Since control transfers over time, revenue is recognized based on the extent of progress towards completion of the single performance obligation. Fuel Tech uses the cost-to-cost input measure of progress for our contracts since it best depicts the transfer of assets to the customer which occurs as we incur costs on our contracts. Under the cost-to-cost input measure of progress, the extent of progress towards completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. Revenues are recorded proportionally as costs are incurred. Costs to fulfill include all internal and external engineering costs, equipment charges, inbound and outbound freight expenses, internal and site transfer costs, installation charges, purchasing and receiving costs, inspection costs, warehousing costs, project personnel travel expenses and other direct and indirect expenses specifically identified as project- or product-line related, as appropriate (e.g. test equipment depreciation and certain insurance expenses).

Fuel Tech’s APC product line also includes ancillary revenue for post contractual goods and services. Revenue associated with these activities are recognized at point in time when delivery of goods or completion of the service obligation is performed.

Fuel Tech normally provides performance guarantees to our customers based on the operating conditions for the project. As part of the project implementation process, we perform system start-up and optimization services that effectively serve as a test of actual project performance. We believe that this test, combined with the accuracy of the modeling that is performed, enables revenue to be recognized prior to the receipt of formal customer acceptance.

FUEL CHEM

Revenues from the sale of chemical products are recognized when control transfers to customer upon shipment or delivery of the product based on the applicable shipping terms. We generally recognize revenue for these arrangements at a point in time based on our evaluation of when the customer obtains control of the promised goods or services. 

On occasion, Fuel Tech will engineer and sell its chemical pumping equipment.  These projects are similar in nature to the APC projects described above and for those projects where control transfers over time, revenue is recognized based on the extent of progress towards completion of the single performance obligation. 

For projects containing multiple performance obligations, the Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.

Cost of Goods and Service [Policy Text Block]

Cost of Sales

Cost of sales includes all internal and external engineering costs, equipment and chemical charges, inbound and outbound freight expenses, internal and site transfer costs, installation charges, purchasing and receiving costs, inspection costs, warehousing costs, project personnel travel expenses and other direct and indirect expenses specifically identified as project- or product line-related, as appropriate (e.g., test equipment depreciation and certain insurance expenses). Certain depreciation and amortization expenses related to tangible and intangible assets, respectively, are allocated to cost of sales. We classify shipping and handling costs in cost of sales in the consolidated statements of operations.

Selling, General and Administrative Expenses, Policy [Policy Text Block]

Selling, General and Administrative Expenses

Selling, general and administrative expenses primarily include the following categories except where an allocation to the cost of sales line item is warranted due to the project- or product-line nature of a portion of the expense category: salaries and wages, employee benefits, non-project travel, insurance, legal, rent, accounting and auditing, recruiting, telephony, employee training, Board of Directors’ fees, auto rental, office supplies, dues and subscriptions, utilities, real estate taxes, commissions and bonuses, marketing materials, postage and business taxes. Departments comprising the selling, general and administrative line item primarily include the functions of executive management, finance and accounting, investor relations, regulatory affairs, marketing, business development, information technology, human resources, sales, legal and general administration.

Income Tax, Policy [Policy Text Block]

Income Taxes

The provision for income taxes is determined using the asset and liability approach of accounting for income taxes. Under this approach, the provision for income taxes represents income taxes paid or payable (or received or receivable) for the current year plus the change in deferred taxes during the year. Deferred taxes represent the future tax consequences expected to occur when the reported amounts of assets and liabilities are recovered or paid, and result from differences between the financial and tax bases of our assets and liabilities and are adjusted for changes in tax rates and tax laws when enacted. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized. In evaluating the need for a valuation allowance, management considers all potential sources of taxable income, including income available in carryback periods, future reversals of taxable temporary differences, projections of taxable income, and income from tax planning strategies, as well as all available positive and negative evidence. Positive evidence includes factors such as a history of profitable operations, projections of future profitability within the carryforward period, including from tax planning strategies, and our experience with similar operations. Negative evidence includes items such as cumulative losses, projections of future losses, or carryforward periods that are not long enough to allow for the utilization of a deferred tax asset based on existing projections of income. Deferred tax assets for which no valuation allowance is recorded may not be realized upon changes in facts and circumstances.

Tax benefits related to uncertain tax positions taken or expected to be taken on a tax return are recorded when such benefits meet a more likely than not threshold. Otherwise, these tax benefits are recorded when a tax position has been effectively settled, which means that the statute of limitation has expired or the appropriate taxing authority has completed their examination even though the statute of limitations remains open. Interest and penalties related to uncertain tax positions are recognized as part of the provision for income taxes and are accrued beginning in the period that such interest and penalties would be applicable under relevant tax law until such time that the related tax benefits are recognized.

Lessee, Leases [Policy Text Block]

Leases

The Company applies the provisions of ASC 842, Leases. The Company determines if an arrangement is a lease at inception by evaluating whether the arrangement conveys the right to use an identified asset and whether the Company obtains substantially all of the economic benefits from and has the ability to direct the use of the asset. Right-of-use (ROU) assets and lease liabilities are recognized at the lease commencement date based on the present value of the future minimum lease payments over the lease term. Operating ROU assets also include the impact of any lease incentives. Operating leases are included in right-of-use operating lease assets, operating lease liabilities - current, and operating lease liabilities - non-current on our Consolidated Balance Sheets.

Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The operating lease ROU asset also includes any lease payments made and excludes lease incentives and initial direct costs incurred. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term.

We have lease agreements with lease and non-lease components, and we elected the practical expedient to not separate lease and non-lease components for the majority of our leases. For certain equipment leases, such as vehicles, we account for the lease and non-lease components as a single lease component. We also elected the practical expedient for leases with an initial term of 12 months or less.

Share-Based Payment Arrangement [Policy Text Block]

Stock-Based Compensation

Our stock-based employee compensation plan, referred to as the Fuel Tech, Inc. 2014 Long-Term Incentive Plan (Incentive Plan), was adopted in May 2014 and allows for awards to be granted to participants in the form of non-qualified stock options, incentive stock options, stock appreciation rights, restricted stock, restricted stock units, performance awards, and bonuses or other forms of share-based or non-share-based awards or combinations thereof. Participants in the Incentive Plan may be our directors, officers, employees, consultants or advisors (except consultants or advisors in capital-raising transactions) as the directors determine are key to the success of our business. There are a maximum of 5,884,076 shares that may be issued or reserved for awards to participants under the Incentive Plan as of December 31, 2023. Based on the existing issued or reserved awards in Incentive Plan, there are 645,650 shares available to be used for future awards to participants in the Incentive Plan as of December 31, 2023.

Pension and Other Postretirement Plans, Nonpension Benefits, Policy [Policy Text Block]

Defined Contribution Plan

We have a retirement savings plan available for all our U.S. employees who have met minimum length-of-service requirements. Our contributions are determined based upon amounts contributed by the employees with additional contributions made at the discretion of the Board of Directors. Costs related to this plan were $233 and $200 in 2023 and 2022, respectively.

Earnings Per Share, Policy [Policy Text Block]

Basic and Diluted Earnings per Common Share

Basic earnings per share excludes the antidilutive effects of stock options, restricted stock units (RSUs), warrants, and the nil coupon non-redeemable convertible unsecured loan notes (see Note 6). Diluted earnings per share includes the dilutive effect of the nil coupon non-redeemable convertible unsecured loan notes, RSUs, warrants, and unexercised in-the-money stock options, except in periods of net loss where the effect of these instruments is antidilutive. Out-of-the-money stock options and warrants are excluded from diluted earnings per share because they are unlikely to be exercised and would be anti-dilutive if they were exercised. At December 31, 2023 and 2022, basic earnings per share is equal to diluted earnings per share because all outstanding stock awards, warrants, and convertible loan notes are considered anti-dilutive during periods of net loss. At December 31, 2023 and 2022, we had weighted-average outstanding equity awards of 390,900 and 763,800, respectively, and 2,850,000 warrants in both periods, which were antidilutive or represent out-of-the-money options for the purpose of calculation of the diluted earnings per share. As of December 31, 2023 and 2022, 246,500 and 42,600 incremental equity awards were antidilutive because of the net loss in the year then ended, respectively. These equity awards could potentially dilute basic EPS in future years.

The table below sets forth the weighted-average shares used at December 31 in calculating earnings (loss) per share:

	2023		2022
Basic weighted-average shares		30,348,000		30,289,000
Conversion of unsecured loan notes		—		—
Unexercised options and unvested restricted stock units		—		—
Diluted weighted-average shares		30,348,000		30,289,000

Concentration Risk, Credit Risk, Policy [Policy Text Block]

Risk Concentrations

Financial instruments that potentially subject the Company to a significant concentration of credit risk consist primarily of cash and cash equivalents and accounts receivable. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. However, management believes the Company is not exposed to significant credit risk due to the financial position of its primary depository institution where a significant portion of its deposits are held.

For the year ended December 31, 2023, we had two customers which individually represented greater than 10% of revenues. These two customers contributed revenues to the FUEL CHEM technology segment. In total these two customers represented 36% of consolidated revenues. We had no customer that accounted for greater than 10% of our current assets as of December 31, 2023.

For the year ended December 31, 2022, we had three customers which individually represented greater than 10% of revenues. Two customers primarily contributed revenues to the FUEL CHEM technology segment and one contributed revenue to the APC technology segment. In total these three customers represented 48% of consolidated revenues. We had no customer that accounted for greater than 10% of our current assets as of December 31, 2022.

We control credit risk through requiring milestone payments on long-term contracts, performing ongoing credit evaluations of its customers, and in some cases obtaining security for payment through bank guarantees and letters of credit.

Our FUEL CHEM technology segment is dependent, in part, upon a supply of magnesium hydroxide. Any adverse changes in the availability of this chemical will likely have an adverse impact on ongoing operation of our FUEL CHEM programs. Our supplier of magnesium hydroxide, Martin Marietta Magnesia Specialties, LLC (MMMS) assures the continuance of a stable supply from MMMS of magnesium hydroxide products for our requirements in the U.S. and Canada. MMMS supplies us with magnesium hydroxide products manufactured pursuant to our specifications and we have agreed to purchase from MMMS, and MMMS has agreed to supply, 100% of our requirements for such magnesium hydroxide products for our customers who purchase such products for delivery in the U.S. and Canada. There can be no assurance that we will be able to obtain a stable source of magnesium hydroxide in markets outside the U.S.

Stockholders' Equity, Policy [Policy Text Block]

Treasury Stock

We use the cost method to account for common stock repurchases. During the years ended December 31, 2023 and 2022, we withheld 0 and 12,497 shares of our common stock, valued at approximately $0 and $17, respectively, to settle personal tax withholding obligations that arose as a result of restricted stock units that vested. Refer to Note 5, “Treasury Stock,” for further discussion.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently Issued Accounting Pronouncements

In November 2023, the FASB issued ASU 2023- 07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which provides guidance for additional disclosures around segment reporting. The standard will become effective for annual periods beginning on January 1, 2024 for Fuel Tech and for interim periods thereafter. Application of the amendments is retrospective. The Company is reviewing the impact of this new pronouncement and expects to incorporate the additional disclosures in the Segment note when the ASU is adopted. 

In December 2023, the FASB issued ASU 2023- 09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which provides guidance for additional disclosures around the tax rate reconciliation and other tax disclosures. The standard will become effective for annual periods beginning on January 1, 2025 for Fuel Tech. Application of the amendments should be applied prospectively but retrospective application is permitted. The Company is reviewing the impact of this new pronouncement and expects to incorporate the additional disclosures in the Tax note when the ASU is adopted.