| Schedule of Segment Reporting Information, by Segment [Table Text Block] |
| For the year ended December 31, 2025 | | Air Pollution Control Segment | | | FUEL CHEM Segment | | | Other | | | Total | |
| Revenues from external customers | | $ | 8,908 | | | $ | 17,769 | | | $ | — | | | $ | 26,677 | |
| Cost of sales | | | (5,093 | ) | | | (9,201 | ) | | | — | | | | (14,294 | ) |
| Gross margin | | | 3,815 | | | | 8,568 | | | | — | | | | 12,383 | |
| Selling, general and administrative | | | — | | | | — | | | | (14,050 | ) | | | (14,050 | ) |
| Research and development | | | — | | | | — | | | | (2,014 | ) | | | (2,014 | ) |
| Operating income (loss) from continuing operations | | $ | 3,815 | | | $ | 8,568 | | | $ | (16,064 | ) | | $ | (3,681 | ) |
| For the year ended December 31, 2024 | | Air Pollution Control Segment | | | FUEL CHEM Segment | | | Other | | | Total | |
| Revenues from external customers | | $ | 11,242 | | | $ | 13,891 | | | $ | — | | | $ | 25,133 | |
| Cost of sales | | | (7,050 | ) | | | (7,460 | ) | | | — | | | | (14,510 | ) |
| Gross margin | | | 4,192 | | | | 6,431 | | | | — | | | | 10,623 | |
| Selling, general and administrative | | | — | | | | — | | | | (13,761 | ) | | | (13,761 | ) |
| Research and development | | | — | | | | — | | | | (1,564 | ) | | | (1,564 | ) |
| Operating income (loss) from continuing operations | | $ | 4,192 | | | $ | 6,431 | | | $ | (15,325 | ) | | $ | (4,702 | ) |
|
| Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] |
| For the years ended December 31, | | 2025 | | | 2024 | |
| Revenues: | | | | | | | | |
| United States | | $ | 21,022 | | | $ | 17,802 | |
| Other Foreign | | | 5,655 | | | | 7,331 | |
| | | $ | 26,677 | | | $ | 25,133 | |
| As of December 31, | | 2025 | | | 2024 | |
| Assets: | | | | | | | | |
| United States | | $ | 44,345 | | | $ | 44,430 | |
| Foreign | | | 2,834 | | | | 4,367 | |
| | | $ | 47,179 | | | $ | 48,797 | |
|