Financial assets and liabilities are initially recorded at fair value. The carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts receivable, accounts payable and accrued expenses, are carried at cost which approximates fair value due to the short-term maturity of these instruments and are Level 1 assets or liabilities of the fair value hierarchy.

The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received in the sale of an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows:

Level 1 ‑ Inputs are unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2 ‑ Inputs are other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).

Level 3 ‑ Inputs are unobservable and reflect the Company’s assumptions that market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

The Company’s derivative liability embedded in its September 2019 Financing Agreement related to the mandatory prepayment feature is measured at fair value using a probability-weighted discounted cash flow model and is classified as a Level 3 liability

of the fair value hierarchy due to the use of significant unobservable inputs. The liability is presented as an embedded derivative liability on the consolidated balance sheets and is subject to remeasurement to fair value at the end of each reporting period, with the change in fair value recognized as a component of other expense in its consolidated statements of operations. The assumptions used in the discounted cash flow model include: (1) management's estimates of the probability and timing of future cash flows and related events; (2) the Company's risk-adjusted discount rate that includes a company-specific risk premium; and (3) the Company's cost of debt.

The Company's liability-classified warrants issued with an exercise price of $0.01 per share are measured at fair value using the Black-Scholes option-pricing model and are classified as a Level 3 liability of the fair value hierarchy due to the use of significant unobservable inputs. The warrant liabilities are presented as current liabilities on the consolidated balance sheets and are subject to remeasurement to fair value at the end of each reporting period, with the change in fair value recognized as a component of other income (expense) in its consolidated statements of operations. The inputs and assumptions used in the Black-Scholes option-pricing model include: (1) the Company's stock price; (2) the exercise price of the warrant; (3) the expected term of the warrant; (4) the Company's expected stock price volatility; (5) the Company's expected dividends; and (6) the risk-free interest rate.

The Company's liability-classified warrants issued with an exercise price greater than $0.01 per share are measured at fair value using the Monte Carlo simulation model and are classified as a Level 3 liability of the fair value hierarchy due to the use of significant unobservable inputs. The warrant liabilities are presented as current liabilities on the consolidated balance sheets and are subject to remeasurement to fair value at the end of each reporting period, with the change in fair value recognized as a component of other income (expense) or as compensation expense in its consolidated statements of operations. The inputs and assumptions used in the Monte Carlo model include: (1) the Company's stock price; (2) the Company's expected stock price volatility; and (3) the risk-free interest rate.

The following table provides a reconciliation for the opening and closing balances of both liabilities from December 31, 2019 to December 31, 2021:


($ in thousands)	Derivative Liability			Warrant Liabilities
Balance at December 31, 2019	$	1,021		$	—
Issuances		—			13,239
Net change in fair value		1,257			(1,975	)
Balance at December 31, 2020		2,278			11,264
Issuances		—			—
Net change in fair value		(765	)		2,520
Balance at December 31, 2021	$	1,513		$	13,784

There were no transfers between Level 1, Level 2, and Level 3 during the periods presented.

The Company’s obligations under its debt agreements are carried at amortized cost. The fair value of the Company’s obligations under its convertible notes and the Term Loans under the Antara Financing Agreement are considered Level 3 liabilities of the fair value hierarchy because fair value was estimated using significant unobservable inputs. The fair value of the Company’s other debt arrangements are considered Level 2 liabilities of the fair value hierarchy because fair value is estimated using inputs other than quoted prices that are observable for the liability such as interest rates and yield curves. The estimated fair value of the Company's Term Loans under the Antara Financing Agreement was $9.7 million as of December 31, 2021, and its carrying value was $17.7 million as of December 31, 2021. The estimated fair value of the Company's Term Loans under the Antara Financing Agreement was $15.9 million as of December 31, 2020, and its carrying value was $31.6 million as of December 31, 2020. The carrying value of the Company’s remaining debt obligations approximates their fair value and was $49.0 million and $59.0 million at December 31, 2021 and 2020, respectively.

Certain non-financial assets, primarily property and equipment, lease right-of-use assets, goodwill and intangible assets, are not required to be measured at fair value on a recurring basis and are reported at carrying value. However, these assets are required to be assessed for impairment whenever events or circumstances indicate that their carrying value may not be fully recoverable, and at least annually for goodwill. In the event an impairment is required, the asset is adjusted to fair value, using market-based assumptions.

During the year ended December 31, 2020, the Company recorded a $2.3 million impairment charge relating to the CNG Fueling Stations asset group. This impairment is recorded in the Impairment of long-lived assets line item in the consolidated statement of operations.

Our impairment testing of long-lived assets utilizes significant unobservable inputs (Level 3) to determine fair value. When quoted market prices are not available, the fair value of an asset group for long-lived asset impairment testing is determined using primarily an income approach. The income approach is based on projected future (debt-free) cash flows that are discounted to present value. The appropriate discount rate is based on the asset group’s weighted-average cost of capital that takes market participant assumptions into consideration.

Management’s cash flow forecast used in these valuations were developed in conjunction with management’s periodically updated cash flow and profitability forecasts and its resulting revised outlook for business performance, including consideration of recent performance and trends, the projected impact of the COVID-19 pandemic, strategic initiatives, and industry trends. Assumptions used in the valuations are similar to those that would be used by market participants performing an independent valuation of the asset group. The evaluation of asset impairment requires the Company to make assumptions about future cash flows over the life of the asset being evaluated. These assumptions require significant judgment and actual results may differ from assumed and estimated amounts.