Are some emergent properties non-falsifiable as a causal necessity by science? Since we cannot determine why emergent properties are what they are from physics and chemistry laws, I am guessing that we cannot determine what other alternatives there can exist or be in this world or another world. Is this correct? One example, is whether there can be silicon-based lifeform on other planets by just looking at the laws of physics and chemistry alone. The only way to falsify it would be to observe a silicon-based lifeform, but aside that from the "higher" sciences, it's not falsifiable.
If you clarify what you mean by 'every emergent property' your question will answer itself.
Clearly every observable emergent property is non-falsifiable because it exists.
So what remains are proposed or imaginary emergent properties that have never been observed. We can certainly rule some of those out from fundamental scientific considerations- to take an extreme example, we can rule out the possibility of aliens made only of protons. If you rule that out as a silly example, then you must clarify what you mean by 'every emergent property'. If you say to me that you didn't intend the phrase to include emergent properties that are clearly impossible, then what you seem to be asking is whether possible emergent properties are falsifiable, and the answer to that seems to be no by definition.
A good way to ask about the limits of reductionism. My hunch is the notion of emergence is reductionist in spirit. Like how Adrian Monk, from the detective series, is wont to say "He's the guy. I know he did it, I just don't know how., we're supposed to think emergent phenomena like life and consciousness are physical, we just don't know how.
In theoretical discourse, an emergent property is a property that arises in one ontology that can be seen as not being able to be reduced in another. That doesn't mean the property is beyond a physicalist model, but rather seems to appear without an adequate grounding. Let's give an example.
Clearly there is a relationship between the ontology of biology and psychology. It is rather orthodox to accept that the biological constituents of the brain are correlated with human thought and consciousness. These are called neural correlates of consciousness. You apply voltage to a person's brain in surgery, and they giggle. Ask them why, and they'll just tell you there's an urge. And yet, consciousness, as it is typically construed by philosophers is irreducible to the anatomy and physiology of the brain. There is a certain je nai se quois about consciousness that makes it seem that there's an emergence of consciousness from the brain that isn't strictly causal. In fact, there's a deep and perplexing mystery that David Chalmers characterized as the hard problem of consciousness (which is above and beyond the easy problem of understanding how it results from the neurons firing).
So, if as a philosopher you believe that consciousness supervenes on brain activity, then you are struck with the fact that consciousness doesn't completely or even mostly reduce to neural anatomy and computation.
Does that mean consciousness doesn't exist and one can't determine if a rock is conscious? Of course not, forensic psychologists everyday are employed by the court to evaluate the nature of someone's mental states. Some people who pose an immediate danger to themselves and others can be institutionalized on the basis of their inferred conscious states. And of course, no psychologist would attribute the property and the dispositions related to consciousness to a rock.
This is not what "falsifiable" means. Falsification does not refer to ruling out phenomena based on known scientific theories (and since all theories are only provisional science cannot rule out anything with certainty anyway), it refers to ruling out theories based on observed phenomena. And any theory that proposes emergent properties with empirical consequences is surely falsifiable (some have already been falsified). – Conifold
Now, consciousness as a property is not falsified, it is detected or not detected, and the means of doing so is a diagnostic. For instance, psychologists will ask patients a series of questions. For a non-responsive patient, a psychiatrist may be brought in to check for serious neurological problems. And a patient in a coma may or may not be conscious based on the brain activity detected by neuroimaging and interpreted by a neurologist under the guidance of an MD. So, detecting a property (see operational definition for abstract properties) is different than falsifying an explanation about it. For instance, modern science has falsified the idea that consciousness results from élan vital.
To "falsify" only has meaning with respect to a scientific theory. When scientists create a theory, initially it is just words on paper - it has no particular meaning.
A proper scientific theory must include within it a way to tell whether it is wrong along with it's main content - i.e., any explanation or prediction about reality it offers. This is what is meant by "falsifiable". To be found "false" then means that the theory (or parts of it) is rubbish and needs to be thrown out (or amended to circumvent the particular falsehood, if possible). And finally, the way to tell whether it is false must stem from reality - i.e., an experiment or observation.
To be false, said experiment or observation will conflict with the explanations or predictions offered by the theory, and reality always wins.
The term "non-falsifiable" in this context means that the theory in question does not come with some way to falsify it. This means that the theory can be abandoned right away without much ado - it is scientifically worthless except maybe as idle speculation or science-fiction entertainment (or to be very generous, as food-for-thought or inspirations for future theories).
To address some of your words:
Are some emergent properties non-falsifiable
The term "falsifiable" in this context only makes sense for scientific theories. Properties are not theories.
"Emergent properties" - emergence means structures or behavior appearing in a complex system as a whole without immediately being attributable to any single part of the system, i.e., the emergent property is a new category which has no equivalence in any part of the system. Their concrete behavior may be hard or impossible to explain or predict (see an extremely simple example: bifurcation), but if it happens, it is still part of reality and not better or worse than any other part.
whether there can be silicon-based lifeform on other planets by just looking at the laws of physics and chemistry alone
There could very well be a proper scientific theory which rules out the existence of silicon-based lifeforms in the universe based only on our arbitrary definition of "life" and the physical properties of silicon. Its falsifiability stems inherently from the fact that even a single observation of silicon-based life would make it false. While at the moment we are hardly capable of making such an observation (our telescopes and space-ships are not there yet), eventually we might, and if silicon-based lifeforms exist then it is just a question of probability or time until we'd find one, if we evolve to a galactic species.
Obversely, there can never be a scientific theory which says "there can be a silicon life-form somewhere in the universe" simply because it would not be falsifiable. We can not check the whole universe for said lifeforms to make sure we don't find any, and even if we could, that would still not prove that none will appear in the future. Note that there is no philosophical content here - it is simply the practical impossibility of falsifying it that takes it from a scientific theory down to irrelevance.