Waste disposal, sometimes including the injection of waste fluids, is part of the hydraulic fracturing process. We speak of "nuclear power" and "hydraulic fracturing" as broader terms encompassing more than just the core of power generation or fracturing of rock.
It's obvious to anyone without blinders that's what Holland was referring to.
If you are talking about disposal of produced water (saltwater), all fraccing does is enhance production. That saltwater would have been produced with oil from the formation as part of the produced fluids anyway, provided the well had even been economic (vertical or horizontal) without fraccing the formation, which has been pretty much an industry standard to enable or enhance production for 80 years.
Let's break this down.
Drilling fluids used while drilling are commonly re-used or even sold to other companies drilling in the area.
Frac fluids are used to fracture the formation after drilling is completed and are mostly produced back in the flowback period, (initial production), and either saved and treated for re-use, or disposed of. Currently the trend is for re-use as an economic measure.
Produced water is also disposed of, this being water from the reservoir which also contained oil and/or gas. This water is usually saline and disposed of in injection wells.
All hydraulic fracturing does is enhance flow rates from the formation the oil and produced water are produced from. That produced water would have been disposed of in an injection well, anyway. That's a production thing, not really a fraccing thing.
Aside from the oil and gas production industry, other industries use injection wells to dispose of fluids it is far more expensive or dangerous to treat than to just inject into a rock formation at depth. The first example I provided of injection wells being identified as a cause of seismic activity was in Colorado at a nuclear weapons manufacturing facility and had nothing to do with the oil industry.
In cases where seismic activity is tied to wastewater disposal, that will be dependent on local geology and the rate and volume of wastewater being injected. Some will show a cause-effect relationship, others will not, and some will show no effect at all.
